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	$53.90	10.213%	$59.4048	$59.40	$59.40	$59.40
Purchase #2	$110.50	3.701%	$114.5896	$114.59	$114.60	$114.60
Purchase #3	$57.73	3.270%	$59.6178	$59.62	$59.60	$59.60
Purchase #4	$111.54	6.174%	$118.4265	$118.43	$118.45	$118.40
Purchase #5	$203.77	9.317%	$222.7553	$222.76	$222.75	$222.80
Purchase #6	$52.57	11.775%	$58.7601	$58.76	$58.75	$58.80
Purchase #7	$234.26	7.286%	$251.3282	$251.33	$251.35	$251.30
7 purchase totals =	$824.27		$884.8823	$884.89	$884.90	$884.90