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	$140.51	9.444%	$153.7798	$153.78	$153.80	$153.80
Purchase #2	$149.25	7.319%	$160.1736	$160.17	$160.15	$160.20
Purchase #3	$114.33	11.349%	$127.3053	$127.31	$127.30	$127.30
Purchase #4	$168.78	4.650%	$176.6283	$176.63	$176.65	$176.60
Purchase #5	$102.88	10.548%	$113.7318	$113.73	$113.75	$113.70
Purchase #6	$141.54	13.403%	$160.5106	$160.51	$160.50	$160.50
Purchase #7	$136.25	4.199%	$141.9711	$141.97	$141.95	$142.00
7 purchase totals =	$953.54		$1,034.1005	$1,034.10	$1,034.10	$1,034.10