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	$195.52	7.622%	$210.4225	$210.42	$210.40	$210.40
Purchase #2	$90.49	9.551%	$99.1327	$99.13	$99.15	$99.10
Purchase #3	$16.53	9.634%	$18.1225	$18.12	$18.10	$18.10
Purchase #4	$27.69	3.616%	$28.6913	$28.69	$28.70	$28.70
Purchase #5	$209.39	5.691%	$221.3064	$221.31	$221.30	$221.30
Purchase #6	$103.31	6.349%	$109.8692	$109.87	$109.85	$109.90
Purchase #7	$28.33	11.563%	$31.6058	$31.61	$31.60	$31.60
7 purchase totals =	$671.26		$719.1504	$719.15	$719.10	$719.10