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	$194.92	13.542%	$221.3161	$221.32	$221.30	$221.30
Purchase #2	$92.35	4.492%	$96.4984	$96.50	$96.50	$96.50
Purchase #3	$236.85	8.437%	$256.833	$256.83	$256.85	$256.80
Purchase #4	$153.86	12.223%	$172.6663	$172.67	$172.65	$172.70
Purchase #5	$40.66	3.449%	$42.0624	$42.06	$42.05	$42.10
Purchase #6	$166.35	5.431%	$175.3845	$175.38	$175.40	$175.40
Purchase #7	$240.77	12.387%	$270.5942	$270.59	$270.60	$270.60
7 purchase totals =	$1,125.76		$1,235.3549	$1,235.35	$1,235.35	$1,235.40