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	$70.97	11.482%	$79.1188	$79.12	$79.10	$79.10
Purchase #2	$151.34	6.207%	$160.7337	$160.73	$160.75	$160.70
Purchase #3	$55.48	6.667%	$59.1789	$59.18	$59.20	$59.20
Purchase #4	$191.33	11.727%	$213.7673	$213.77	$213.75	$213.80
Purchase #5	$168.52	4.111%	$175.4479	$175.45	$175.45	$175.40
Purchase #6	$38.89	8.166%	$42.0658	$42.07	$42.05	$42.10
Purchase #7	$40.83	7.257%	$43.793	$43.79	$43.80	$43.80
7 purchase totals =	$717.36		$774.1054	$774.11	$774.10	$774.10