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	$183.38	6.428%	$195.1677	$195.17	$195.15	$195.20
Purchase #2	$20.78	5.377%	$21.8973	$21.90	$21.90	$21.90
Purchase #3	$103.75	5.177%	$109.1211	$109.12	$109.10	$109.10
Purchase #4	$61.74	6.367%	$65.671	$65.67	$65.65	$65.70
Purchase #5	$65.38	9.319%	$71.4728	$71.47	$71.45	$71.50
Purchase #6	$100.70	5.425%	$106.163	$106.16	$106.15	$106.20
Purchase #7	$25.45	6.526%	$27.1109	$27.11	$27.10	$27.10
7 purchase totals =	$561.18		$596.6038	$596.60	$596.50	$596.70