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	$136.65	4.422%	$142.6927	$142.69	$142.70	$142.70
Purchase #2	$111.56	4.522%	$116.6047	$116.60	$116.60	$116.60
Purchase #3	$135.37	12.601%	$152.428	$152.43	$152.45	$152.40
Purchase #4	$247.97	7.600%	$266.8157	$266.82	$266.80	$266.80
Purchase #5	$133.65	13.114%	$151.1769	$151.18	$151.20	$151.20
Purchase #6	$91.33	6.418%	$97.1916	$97.19	$97.20	$97.20
Purchase #7	$88.51	12.834%	$99.8694	$99.87	$99.85	$99.90
7 purchase totals =	$945.04		$1,026.7790	$1,026.78	$1,026.80	$1,026.80