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	$50.30	8.373%	$54.5116	$54.51	$54.50	$54.50
Purchase #2	$214.58	13.575%	$243.7092	$243.71	$243.70	$243.70
Purchase #3	$69.84	3.841%	$72.5226	$72.52	$72.50	$72.50
Purchase #4	$225.70	5.697%	$238.5581	$238.56	$238.55	$238.60
Purchase #5	$152.92	4.401%	$159.65	$159.65	$159.65	$159.70
Purchase #6	$126.63	10.453%	$139.8666	$139.87	$139.85	$139.90
Purchase #7	$91.29	5.859%	$96.6387	$96.64	$96.65	$96.60
7 purchase totals =	$931.26		$1,005.4568	$1,005.46	$1,005.40	$1,005.50