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	$188.53	6.546%	$200.8712	$200.87	$200.85	$200.90
Purchase #2	$238.72	10.815%	$264.5376	$264.54	$264.55	$264.50
Purchase #3	$22.69	11.114%	$25.2118	$25.21	$25.20	$25.20
Purchase #4	$227.62	11.175%	$253.0565	$253.06	$253.05	$253.10
Purchase #5	$73.68	13.600%	$83.7005	$83.70	$83.70	$83.70
Purchase #6	$107.29	10.838%	$118.9181	$118.92	$118.90	$118.90
Purchase #7	$67.42	4.302%	$70.3204	$70.32	$70.30	$70.30
7 purchase totals =	$925.95		$1,016.6161	$1,016.62	$1,016.55	$1,016.60