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	$154.86	11.369%	$172.466	$172.47	$172.45	$172.50
Purchase #2	$172.39	9.251%	$188.3378	$188.34	$188.35	$188.30
Purchase #3	$92.36	4.766%	$96.7619	$96.76	$96.75	$96.80
Purchase #4	$90.98	7.313%	$97.6334	$97.63	$97.65	$97.60
Purchase #5	$156.49	4.689%	$163.8278	$163.83	$163.85	$163.80
Purchase #6	$137.87	10.628%	$152.5228	$152.52	$152.50	$152.50
Purchase #7	$134.71	12.166%	$151.0988	$151.10	$151.10	$151.10
7 purchase totals =	$939.66		$1,022.6485	$1,022.65	$1,022.65	$1,022.60