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	$125.27	13.845%	$142.6136	$142.61	$142.60	$142.60
Purchase #2	$79.46	11.846%	$88.8728	$88.87	$88.85	$88.90
Purchase #3	$212.50	4.145%	$221.3081	$221.31	$221.30	$221.30
Purchase #4	$58.85	5.869%	$62.3039	$62.30	$62.30	$62.30
Purchase #5	$155.42	12.136%	$174.2818	$174.28	$174.30	$174.30
Purchase #6	$145.82	3.483%	$150.8989	$150.90	$150.90	$150.90
Purchase #7	$96.67	10.502%	$106.8223	$106.82	$106.80	$106.80
7 purchase totals =	$873.99		$947.1014	$947.09	$947.05	$947.10