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	$245.50	7.241%	$263.2767	$263.28	$263.30	$263.30
Purchase #2	$30.68	5.345%	$32.3198	$32.32	$32.30	$32.30
Purchase #3	$240.36	6.210%	$255.2864	$255.29	$255.30	$255.30
Purchase #4	$162.71	8.267%	$176.1612	$176.16	$176.15	$176.20
Purchase #5	$219.55	10.463%	$242.5215	$242.52	$242.50	$242.50
Purchase #6	$58.77	9.413%	$64.302	$64.30	$64.30	$64.30
Purchase #7	$65.53	10.872%	$72.6544	$72.65	$72.65	$72.70
7 purchase totals =	$1,023.10		$1,106.5220	$1,106.52	$1,106.50	$1,106.60