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	$229.87	11.643%	$256.6338	$256.63	$256.65	$256.60
Purchase #2	$19.77	4.466%	$20.6529	$20.65	$20.65	$20.70
Purchase #3	$137.85	6.147%	$146.3236	$146.32	$146.30	$146.30
Purchase #4	$222.57	5.541%	$234.9026	$234.90	$234.90	$234.90
Purchase #5	$103.85	6.226%	$110.3157	$110.32	$110.30	$110.30
Purchase #6	$145.96	12.531%	$164.2502	$164.25	$164.25	$164.30
Purchase #7	$80.41	12.369%	$90.3559	$90.36	$90.35	$90.40
7 purchase totals =	$940.28		$1,023.4347	$1,023.43	$1,023.40	$1,023.50