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	$38.33	5.170%	$40.3117	$40.31	$40.30	$40.30
Purchase #2	$91.91	7.247%	$98.5707	$98.57	$98.55	$98.60
Purchase #3	$92.76	9.661%	$101.7215	$101.72	$101.70	$101.70
Purchase #4	$89.80	7.223%	$96.2863	$96.29	$96.30	$96.30
Purchase #5	$99.25	12.485%	$111.6414	$111.64	$111.65	$111.60
Purchase #6	$227.62	10.668%	$251.9025	$251.90	$251.90	$251.90
Purchase #7	$231.90	3.817%	$240.7516	$240.75	$240.75	$240.80
7 purchase totals =	$871.57		$941.1857	$941.18	$941.15	$941.20