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	$194.91	10.784%	$215.9291	$215.93	$215.95	$215.90
Purchase #2	$56.34	9.743%	$61.8292	$61.83	$61.85	$61.80
Purchase #3	$96.55	8.485%	$104.7423	$104.74	$104.75	$104.70
Purchase #4	$223.33	7.736%	$240.6068	$240.61	$240.60	$240.60
Purchase #5	$132.80	8.797%	$144.4824	$144.48	$144.50	$144.50
Purchase #6	$99.74	9.392%	$109.1076	$109.11	$109.10	$109.10
Purchase #7	$53.95	13.396%	$61.1771	$61.18	$61.20	$61.20
7 purchase totals =	$857.62		$937.8745	$937.88	$937.95	$937.80