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	$152.69	11.356%	$170.0295	$170.03	$170.05	$170.00
Purchase #2	$218.89	10.776%	$242.4776	$242.48	$242.50	$242.50
Purchase #3	$65.96	11.109%	$73.2875	$73.29	$73.30	$73.30
Purchase #4	$239.63	4.797%	$251.1251	$251.13	$251.15	$251.10
Purchase #5	$171.83	10.741%	$190.2863	$190.29	$190.30	$190.30
Purchase #6	$118.78	4.847%	$124.5373	$124.54	$124.55	$124.50
Purchase #7	$90.40	8.600%	$98.1744	$98.17	$98.15	$98.20
7 purchase totals =	$1,058.18		$1,149.9177	$1,149.93	$1,150.00	$1,149.90