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	$178.76	7.354%	$191.906	$191.91	$191.90	$191.90
Purchase #2	$102.47	11.504%	$114.2581	$114.26	$114.25	$114.30
Purchase #3	$68.79	3.342%	$71.089	$71.09	$71.10	$71.10
Purchase #4	$36.93	4.412%	$38.5594	$38.56	$38.55	$38.60
Purchase #5	$153.58	7.318%	$164.819	$164.82	$164.80	$164.80
Purchase #6	$111.42	6.736%	$118.9253	$118.93	$118.95	$118.90
Purchase #7	$101.87	6.338%	$108.3265	$108.33	$108.35	$108.30
7 purchase totals =	$753.82		$807.8833	$807.90	$807.90	$807.90