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	$43.88	7.833%	$47.3171	$47.32	$47.30	$47.30
Purchase #2	$46.74	3.608%	$48.4264	$48.43	$48.45	$48.40
Purchase #3	$190.46	3.289%	$196.7242	$196.72	$196.70	$196.70
Purchase #4	$10.59	10.834%	$11.7373	$11.74	$11.75	$11.70
Purchase #5	$53.30	12.503%	$59.9641	$59.96	$59.95	$60.00
Purchase #6	$154.75	6.713%	$165.1384	$165.14	$165.15	$165.10
Purchase #7	$234.41	7.494%	$251.9767	$251.98	$252.00	$252.00
7 purchase totals =	$734.13		$781.2842	$781.29	$781.30	$781.20