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	$175.81	7.433%	$188.878	$188.88	$188.90	$188.90
Purchase #2	$200.28	7.694%	$215.6895	$215.69	$215.70	$215.70
Purchase #3	$131.34	4.561%	$137.3304	$137.33	$137.35	$137.30
Purchase #4	$91.77	12.550%	$103.2871	$103.29	$103.30	$103.30
Purchase #5	$245.64	8.211%	$265.8095	$265.81	$265.80	$265.80
Purchase #6	$217.49	12.113%	$243.8346	$243.83	$243.85	$243.80
Purchase #7	$185.59	7.262%	$199.0675	$199.07	$199.05	$199.10
7 purchase totals =	$1,247.92		$1,353.8966	$1,353.90	$1,353.95	$1,353.90