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	$153.25	8.745%	$166.6517	$166.65	$166.65	$166.70
Purchase #2	$91.59	6.562%	$97.6001	$97.60	$97.60	$97.60
Purchase #3	$208.80	6.867%	$223.1383	$223.14	$223.15	$223.10
Purchase #4	$77.56	8.656%	$84.2736	$84.27	$84.25	$84.30
Purchase #5	$71.34	10.251%	$78.6531	$78.65	$78.65	$78.70
Purchase #6	$162.40	12.150%	$182.1316	$182.13	$182.15	$182.10
Purchase #7	$175.61	13.462%	$199.2506	$199.25	$199.25	$199.30
7 purchase totals =	$940.55		$1,031.6990	$1,031.69	$1,031.70	$1,031.80