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	$93.72	12.789%	$105.7059	$105.71	$105.70	$105.70
Purchase #2	$115.27	4.482%	$120.4364	$120.44	$120.45	$120.40
Purchase #3	$113.97	12.403%	$128.1057	$128.11	$128.10	$128.10
Purchase #4	$151.29	13.107%	$171.1196	$171.12	$171.10	$171.10
Purchase #5	$184.96	5.486%	$195.1069	$195.11	$195.10	$195.10
Purchase #6	$19.55	3.369%	$20.2086	$20.21	$20.20	$20.20
Purchase #7	$97.25	6.834%	$103.8961	$103.90	$103.90	$103.90
7 purchase totals =	$776.01		$844.5792	$844.60	$844.55	$844.50