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	$168.38	4.748%	$176.3747	$176.37	$176.35	$176.40
Purchase #2	$64.37	12.497%	$72.4143	$72.41	$72.40	$72.40
Purchase #3	$33.43	11.599%	$37.3075	$37.31	$37.30	$37.30
Purchase #4	$89.40	12.102%	$100.2192	$100.22	$100.20	$100.20
Purchase #5	$8.79	8.552%	$9.5417	$9.54	$9.55	$9.50
Purchase #6	$184.27	13.824%	$209.7435	$209.74	$209.75	$209.70
Purchase #7	$27.63	4.137%	$28.7731	$28.77	$28.75	$28.80
7 purchase totals =	$576.27		$634.3740	$634.36	$634.30	$634.30