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	$35.53	3.472%	$36.7636	$36.76	$36.75	$36.80
Purchase #2	$88.52	12.142%	$99.2681	$99.27	$99.25	$99.30
Purchase #3	$5.27	6.508%	$5.613	$5.61	$5.60	$5.60
Purchase #4	$122.44	5.144%	$128.7383	$128.74	$128.75	$128.70
Purchase #5	$31.38	5.282%	$33.0375	$33.04	$33.05	$33.00
Purchase #6	$82.71	7.140%	$88.6155	$88.62	$88.60	$88.60
Purchase #7	$47.74	8.788%	$51.9354	$51.94	$51.95	$51.90
7 purchase totals =	$413.59		$443.9714	$443.98	$443.95	$443.90