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	$93.40	5.209%	$98.2652	$98.27	$98.25	$98.30
Purchase #2	$29.64	12.419%	$33.321	$33.32	$33.30	$33.30
Purchase #3	$55.45	12.431%	$62.343	$62.34	$62.35	$62.30
Purchase #4	$26.62	13.594%	$30.2387	$30.24	$30.25	$30.20
Purchase #5	$188.70	4.130%	$196.4933	$196.49	$196.50	$196.50
Purchase #6	$79.27	4.855%	$83.1186	$83.12	$83.10	$83.10
Purchase #7	$222.79	9.127%	$243.124	$243.12	$243.10	$243.10
7 purchase totals =	$695.87		$746.9038	$746.90	$746.85	$746.80