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	$44.26	3.613%	$45.8591	$45.86	$45.85	$45.90
Purchase #2	$234.87	4.414%	$245.2372	$245.24	$245.25	$245.20
Purchase #3	$35.38	3.603%	$36.6547	$36.65	$36.65	$36.70
Purchase #4	$148.84	10.830%	$164.9594	$164.96	$164.95	$165.00
Purchase #5	$52.51	6.746%	$56.0523	$56.05	$56.05	$56.10
Purchase #6	$94.38	11.682%	$105.4055	$105.41	$105.40	$105.40
Purchase #7	$142.87	3.304%	$147.5904	$147.59	$147.60	$147.60
7 purchase totals =	$753.11		$801.7586	$801.76	$801.75	$801.90