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	$98.53	11.499%	$109.86	$109.86	$109.85	$109.90
Purchase #2	$216.77	8.251%	$234.6557	$234.66	$234.65	$234.70
Purchase #3	$191.39	3.494%	$198.0772	$198.08	$198.10	$198.10
Purchase #4	$70.80	9.543%	$77.5564	$77.56	$77.55	$77.60
Purchase #5	$52.56	13.610%	$59.7134	$59.71	$59.70	$59.70
Purchase #6	$90.50	3.453%	$93.625	$93.63	$93.65	$93.60
Purchase #7	$196.95	13.632%	$223.7982	$223.80	$223.80	$223.80
7 purchase totals =	$917.50		$997.2859	$997.30	$997.30	$997.40