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	$225.87	8.700%	$245.5207	$245.52	$245.50	$245.50
Purchase #2	$166.61	11.198%	$185.267	$185.27	$185.25	$185.30
Purchase #3	$193.76	3.459%	$200.4622	$200.46	$200.45	$200.50
Purchase #4	$247.69	10.485%	$273.6603	$273.66	$273.65	$273.70
Purchase #5	$84.93	13.303%	$96.2282	$96.23	$96.25	$96.20
Purchase #6	$26.69	9.438%	$29.209	$29.21	$29.20	$29.20
Purchase #7	$81.55	10.786%	$90.346	$90.35	$90.35	$90.30
7 purchase totals =	$1,027.10		$1,120.6934	$1,120.70	$1,120.65	$1,120.70