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	$172.89	10.376%	$190.8291	$190.83	$190.85	$190.80
Purchase #2	$163.44	9.671%	$179.2463	$179.25	$179.25	$179.20
Purchase #3	$209.28	6.655%	$223.2076	$223.21	$223.20	$223.20
Purchase #4	$238.94	10.628%	$264.3345	$264.33	$264.35	$264.30
Purchase #5	$40.92	12.691%	$46.1132	$46.11	$46.10	$46.10
Purchase #6	$91.56	9.321%	$100.0943	$100.09	$100.10	$100.10
Purchase #7	$157.50	10.158%	$173.4989	$173.50	$173.50	$173.50
7 purchase totals =	$1,074.53		$1,177.3239	$1,177.32	$1,177.35	$1,177.20