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	$108.71	3.708%	$112.741	$112.74	$112.75	$112.70
Purchase #2	$20.59	5.775%	$21.7791	$21.78	$21.80	$21.80
Purchase #3	$54.80	13.507%	$62.2018	$62.20	$62.20	$62.20
Purchase #4	$52.54	10.125%	$57.8597	$57.86	$57.85	$57.90
Purchase #5	$196.51	7.596%	$211.4369	$211.44	$211.45	$211.40
Purchase #6	$86.69	11.394%	$96.5675	$96.57	$96.55	$96.60
Purchase #7	$181.55	8.109%	$196.2719	$196.27	$196.25	$196.30
7 purchase totals =	$701.39		$758.8579	$758.86	$758.85	$758.90