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	$105.88	3.243%	$109.3137	$109.31	$109.30	$109.30
Purchase #2	$217.64	5.458%	$229.5188	$229.52	$229.50	$229.50
Purchase #3	$159.66	4.500%	$166.8447	$166.84	$166.85	$166.80
Purchase #4	$73.37	12.471%	$82.52	$82.52	$82.50	$82.50
Purchase #5	$33.35	11.705%	$37.2536	$37.25	$37.25	$37.30
Purchase #6	$189.93	8.732%	$206.5147	$206.51	$206.50	$206.50
Purchase #7	$54.87	13.680%	$62.3762	$62.38	$62.40	$62.40
7 purchase totals =	$834.70		$894.3417	$894.33	$894.30	$894.30