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	$210.74	8.226%	$228.0755	$228.08	$228.10	$228.10
Purchase #2	$190.51	3.245%	$196.692	$196.69	$196.70	$196.70
Purchase #3	$152.67	12.648%	$171.9797	$171.98	$172.00	$172.00
Purchase #4	$82.67	8.542%	$89.7317	$89.73	$89.75	$89.70
Purchase #5	$219.79	4.401%	$229.463	$229.46	$229.45	$229.50
Purchase #6	$124.60	9.479%	$136.4108	$136.41	$136.40	$136.40
Purchase #7	$141.69	12.121%	$158.8642	$158.86	$158.85	$158.90
7 purchase totals =	$1,122.67		$1,211.2169	$1,211.21	$1,211.25	$1,211.30