Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$155.34	12.693%	$175.0573	$175.06	$175.05	$175.10
Purchase #2	$91.36	10.464%	$100.9199	$100.92	$100.90	$100.90
Purchase #3	$199.71	6.294%	$212.2797	$212.28	$212.30	$212.30
Purchase #4	$229.38	4.162%	$238.9268	$238.93	$238.95	$238.90
Purchase #5	$112.47	4.462%	$117.4884	$117.49	$117.50	$117.50
Purchase #6	$235.68	5.128%	$247.7657	$247.77	$247.75	$247.80
Purchase #7	$126.79	3.318%	$130.9969	$131.00	$131.00	$131.00
7 purchase totals =	$1,150.73		$1,223.4347	$1,223.45	$1,223.45	$1,223.50