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	$106.29	11.302%	$118.3029	$118.30	$118.30	$118.30
Purchase #2	$245.65	12.561%	$276.5061	$276.51	$276.50	$276.50
Purchase #3	$88.53	11.713%	$98.8995	$98.90	$98.90	$98.90
Purchase #4	$112.32	7.395%	$120.6261	$120.63	$120.65	$120.60
Purchase #5	$160.71	6.476%	$171.1176	$171.12	$171.10	$171.10
Purchase #6	$187.67	6.742%	$200.3227	$200.32	$200.30	$200.30
Purchase #7	$151.60	9.355%	$165.7822	$165.78	$165.80	$165.80
7 purchase totals =	$1,052.77		$1,151.5571	$1,151.56	$1,151.55	$1,151.50