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	$189.88	11.585%	$211.8776	$211.88	$211.90	$211.90
Purchase #2	$55.53	10.160%	$61.1718	$61.17	$61.15	$61.20
Purchase #3	$75.66	10.144%	$83.335	$83.34	$83.35	$83.30
Purchase #4	$179.89	6.149%	$190.9514	$190.95	$190.95	$191.00
Purchase #5	$76.42	3.293%	$78.9365	$78.94	$78.95	$78.90
Purchase #6	$245.66	5.448%	$259.0436	$259.04	$259.05	$259.00
Purchase #7	$248.79	13.110%	$281.4064	$281.41	$281.40	$281.40
7 purchase totals =	$1,071.83		$1,166.7223	$1,166.73	$1,166.75	$1,166.70