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	$194.88	7.454%	$209.4064	$209.41	$209.40	$209.40
Purchase #2	$59.31	8.112%	$64.1212	$64.12	$64.10	$64.10
Purchase #3	$172.49	6.607%	$183.8864	$183.89	$183.90	$183.90
Purchase #4	$209.60	5.197%	$220.4929	$220.49	$220.50	$220.50
Purchase #5	$145.85	9.581%	$159.8239	$159.82	$159.80	$159.80
Purchase #6	$30.77	9.241%	$33.6135	$33.61	$33.60	$33.60
Purchase #7	$189.95	10.350%	$209.6098	$209.61	$209.60	$209.60
7 purchase totals =	$1,002.85		$1,080.9541	$1,080.95	$1,080.90	$1,080.90