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	$147.54	11.343%	$164.2755	$164.28	$164.30	$164.30
Purchase #2	$52.51	9.535%	$57.5168	$57.52	$57.50	$57.50
Purchase #3	$68.82	4.337%	$71.8047	$71.80	$71.80	$71.80
Purchase #4	$59.52	8.609%	$64.6441	$64.64	$64.65	$64.60
Purchase #5	$19.41	11.711%	$21.6831	$21.68	$21.70	$21.70
Purchase #6	$19.97	4.500%	$20.8687	$20.87	$20.85	$20.90
Purchase #7	$234.74	8.246%	$254.0967	$254.10	$254.10	$254.10
7 purchase totals =	$602.51		$654.8896	$654.89	$654.90	$654.90