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	$143.29	9.797%	$157.3281	$157.33	$157.35	$157.30
Purchase #2	$82.87	10.421%	$91.5059	$91.51	$91.50	$91.50
Purchase #3	$135.90	3.712%	$140.9446	$140.94	$140.95	$140.90
Purchase #4	$99.76	3.596%	$103.3474	$103.35	$103.35	$103.30
Purchase #5	$37.53	3.463%	$38.8297	$38.83	$38.85	$38.80
Purchase #6	$122.58	3.706%	$127.1228	$127.12	$127.10	$127.10
Purchase #7	$75.91	7.432%	$81.5516	$81.55	$81.55	$81.60
7 purchase totals =	$697.84		$740.6301	$740.63	$740.65	$740.50