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	$61.85	4.545%	$64.6611	$64.66	$64.65	$64.70
Purchase #2	$86.80	4.227%	$90.469	$90.47	$90.45	$90.50
Purchase #3	$21.28	11.554%	$23.7387	$23.74	$23.75	$23.70
Purchase #4	$82.28	8.624%	$89.3758	$89.38	$89.40	$89.40
Purchase #5	$87.66	13.486%	$99.4818	$99.48	$99.50	$99.50
Purchase #6	$193.92	11.443%	$216.1103	$216.11	$216.10	$216.10
Purchase #7	$162.29	12.417%	$182.4415	$182.44	$182.45	$182.40
7 purchase totals =	$696.08		$766.2782	$766.28	$766.30	$766.30