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	$94.91	9.873%	$104.2805	$104.28	$104.30	$104.30
Purchase #2	$110.92	11.685%	$123.881	$123.88	$123.90	$123.90
Purchase #3	$128.87	13.119%	$145.7765	$145.78	$145.80	$145.80
Purchase #4	$100.34	12.224%	$112.6056	$112.61	$112.60	$112.60
Purchase #5	$231.60	5.666%	$244.7225	$244.72	$244.70	$244.70
Purchase #6	$180.64	8.435%	$195.877	$195.88	$195.90	$195.90
Purchase #7	$168.73	13.635%	$191.7363	$191.74	$191.75	$191.70
7 purchase totals =	$1,016.01		$1,118.8794	$1,118.89	$1,118.95	$1,118.90