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	$199.87	12.114%	$224.0823	$224.08	$224.10	$224.10
Purchase #2	$55.31	11.430%	$61.6319	$61.63	$61.65	$61.60
Purchase #3	$250.80	5.233%	$263.9244	$263.92	$263.90	$263.90
Purchase #4	$106.96	4.398%	$111.6641	$111.66	$111.65	$111.70
Purchase #5	$225.59	6.119%	$239.3939	$239.39	$239.40	$239.40
Purchase #6	$143.48	8.801%	$156.1077	$156.11	$156.10	$156.10
Purchase #7	$74.45	11.711%	$83.1688	$83.17	$83.15	$83.20
7 purchase totals =	$1,056.46		$1,139.9731	$1,139.96	$1,139.95	$1,140.00