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	$113.32	12.540%	$127.5303	$127.53	$127.55	$127.50
Purchase #2	$97.75	13.693%	$111.1349	$111.13	$111.15	$111.10
Purchase #3	$154.61	10.425%	$170.7281	$170.73	$170.75	$170.70
Purchase #4	$191.87	7.488%	$206.2372	$206.24	$206.25	$206.20
Purchase #5	$167.58	4.338%	$174.8496	$174.85	$174.85	$174.80
Purchase #6	$166.30	3.330%	$171.8378	$171.84	$171.85	$171.80
Purchase #7	$129.75	7.774%	$139.8368	$139.84	$139.85	$139.80
7 purchase totals =	$1,021.18		$1,102.1547	$1,102.16	$1,102.25	$1,101.90