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	$134.97	6.745%	$144.0737	$144.07	$144.05	$144.10
Purchase #2	$188.32	13.286%	$213.3402	$213.34	$213.35	$213.30
Purchase #3	$107.26	4.208%	$111.7735	$111.77	$111.75	$111.80
Purchase #4	$85.42	7.473%	$91.8034	$91.80	$91.80	$91.80
Purchase #5	$199.69	5.325%	$210.3235	$210.32	$210.30	$210.30
Purchase #6	$51.43	3.745%	$53.3561	$53.36	$53.35	$53.40
Purchase #7	$34.27	11.243%	$38.123	$38.12	$38.10	$38.10
7 purchase totals =	$801.36		$862.7934	$862.78	$862.70	$862.80