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	$126.58	6.125%	$134.333	$134.33	$134.35	$134.30
Purchase #2	$145.62	3.138%	$150.1896	$150.19	$150.20	$150.20
Purchase #3	$61.64	4.221%	$64.2418	$64.24	$64.25	$64.20
Purchase #4	$122.80	4.209%	$127.9687	$127.97	$127.95	$128.00
Purchase #5	$43.43	6.384%	$46.2026	$46.20	$46.20	$46.20
Purchase #6	$106.73	4.799%	$111.852	$111.85	$111.85	$111.90
Purchase #7	$161.51	11.516%	$180.1095	$180.11	$180.10	$180.10
7 purchase totals =	$768.31		$814.8972	$814.89	$814.90	$814.90