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	$142.63	5.356%	$150.2693	$150.27	$150.25	$150.30
Purchase #2	$149.59	11.609%	$166.9559	$166.96	$166.95	$167.00
Purchase #3	$72.71	4.738%	$76.155	$76.16	$76.15	$76.20
Purchase #4	$25.50	10.575%	$28.1966	$28.20	$28.20	$28.20
Purchase #5	$43.85	3.467%	$45.3703	$45.37	$45.35	$45.40
Purchase #6	$154.90	10.398%	$171.0065	$171.01	$171.00	$171.00
Purchase #7	$106.55	6.843%	$113.8412	$113.84	$113.85	$113.80
7 purchase totals =	$695.73		$751.7948	$751.81	$751.75	$751.90