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	$209.98	9.475%	$229.8756	$229.88	$229.90	$229.90
Purchase #2	$242.56	6.482%	$258.2827	$258.28	$258.30	$258.30
Purchase #3	$65.93	11.452%	$73.4803	$73.48	$73.50	$73.50
Purchase #4	$162.40	5.867%	$171.928	$171.93	$171.95	$171.90
Purchase #5	$178.39	6.601%	$190.1655	$190.17	$190.15	$190.20
Purchase #6	$110.45	10.178%	$121.6916	$121.69	$121.70	$121.70
Purchase #7	$139.61	8.445%	$151.4001	$151.40	$151.40	$151.40
7 purchase totals =	$1,109.32		$1,196.8238	$1,196.83	$1,196.90	$1,196.90