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	$147.49	12.365%	$165.7271	$165.73	$165.75	$165.70
Purchase #2	$73.70	6.446%	$78.4507	$78.45	$78.45	$78.50
Purchase #3	$113.98	3.370%	$117.8211	$117.82	$117.80	$117.80
Purchase #4	$140.45	7.667%	$151.2183	$151.22	$151.20	$151.20
Purchase #5	$192.67	13.248%	$218.1949	$218.19	$218.20	$218.20
Purchase #6	$141.32	6.285%	$150.202	$150.20	$150.20	$150.20
Purchase #7	$41.53	12.133%	$46.5688	$46.57	$46.55	$46.60
7 purchase totals =	$851.14		$928.1829	$928.18	$928.15	$928.20