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	$182.28	3.182%	$188.0801	$188.08	$188.10	$188.10
Purchase #2	$88.95	11.335%	$99.0325	$99.03	$99.05	$99.00
Purchase #3	$243.71	11.470%	$271.6635	$271.66	$271.65	$271.70
Purchase #4	$101.71	3.492%	$105.2617	$105.26	$105.25	$105.30
Purchase #5	$143.45	6.561%	$152.8618	$152.86	$152.85	$152.90
Purchase #6	$178.38	10.102%	$196.3999	$196.40	$196.40	$196.40
Purchase #7	$106.83	13.436%	$121.1837	$121.18	$121.20	$121.20
7 purchase totals =	$1,045.31		$1,134.4832	$1,134.47	$1,134.50	$1,134.60