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	$149.49	8.807%	$162.6556	$162.66	$162.65	$162.70
Purchase #2	$105.76	9.539%	$115.8484	$115.85	$115.85	$115.80
Purchase #3	$55.34	5.554%	$58.4136	$58.41	$58.40	$58.40
Purchase #4	$145.54	3.208%	$150.2089	$150.21	$150.20	$150.20
Purchase #5	$128.30	13.677%	$145.8476	$145.85	$145.85	$145.80
Purchase #6	$94.90	4.755%	$99.4125	$99.41	$99.40	$99.40
Purchase #7	$25.27	10.816%	$28.0032	$28.00	$28.00	$28.00
7 purchase totals =	$704.60		$760.3898	$760.39	$760.35	$760.30