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	$222.42	9.164%	$242.8026	$242.80	$242.80	$242.80
Purchase #2	$209.28	6.486%	$222.8539	$222.85	$222.85	$222.90
Purchase #3	$42.39	5.251%	$44.6159	$44.62	$44.60	$44.60
Purchase #4	$211.62	12.643%	$238.3751	$238.38	$238.40	$238.40
Purchase #5	$243.64	12.543%	$274.1998	$274.20	$274.20	$274.20
Purchase #6	$10.37	4.536%	$10.8404	$10.84	$10.85	$10.80
Purchase #7	$54.99	11.383%	$61.2495	$61.25	$61.25	$61.20
7 purchase totals =	$994.71		$1,094.9372	$1,094.94	$1,094.95	$1,094.90