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	$192.83	8.730%	$209.6641	$209.66	$209.65	$209.70
Purchase #2	$52.33	5.505%	$55.2108	$55.21	$55.20	$55.20
Purchase #3	$74.52	5.346%	$78.5038	$78.50	$78.50	$78.50
Purchase #4	$110.71	4.317%	$115.4894	$115.49	$115.50	$115.50
Purchase #5	$193.29	6.728%	$206.2946	$206.29	$206.30	$206.30
Purchase #6	$95.88	9.834%	$105.3088	$105.31	$105.30	$105.30
Purchase #7	$158.69	6.143%	$168.4383	$168.44	$168.45	$168.40
7 purchase totals =	$878.25		$938.9098	$938.90	$938.90	$938.90