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	$150.49	5.823%	$159.253	$159.25	$159.25	$159.30
Purchase #2	$226.40	4.743%	$237.1382	$237.14	$237.15	$237.10
Purchase #3	$245.61	11.489%	$273.8281	$273.83	$273.85	$273.80
Purchase #4	$29.90	5.216%	$31.4596	$31.46	$31.45	$31.50
Purchase #5	$150.90	9.451%	$165.1616	$165.16	$165.15	$165.20
Purchase #6	$90.45	12.865%	$102.0864	$102.09	$102.10	$102.10
Purchase #7	$72.65	6.257%	$77.1957	$77.20	$77.20	$77.20
7 purchase totals =	$966.40		$1,046.1226	$1,046.13	$1,046.15	$1,046.20