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	$206.88	6.253%	$219.8162	$219.82	$219.80	$219.80
Purchase #2	$214.68	3.593%	$222.3935	$222.39	$222.40	$222.40
Purchase #3	$31.34	3.423%	$32.4128	$32.41	$32.40	$32.40
Purchase #4	$17.32	8.839%	$18.8509	$18.85	$18.85	$18.90
Purchase #5	$229.78	11.282%	$255.7038	$255.70	$255.70	$255.70
Purchase #6	$190.32	10.187%	$209.7079	$209.71	$209.70	$209.70
Purchase #7	$173.86	12.543%	$195.6673	$195.67	$195.65	$195.70
7 purchase totals =	$1,064.18		$1,154.5524	$1,154.55	$1,154.50	$1,154.60