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	$84.58	13.372%	$95.89	$95.89	$95.90	$95.90
Purchase #2	$22.30	13.740%	$25.364	$25.36	$25.35	$25.40
Purchase #3	$126.47	11.412%	$140.9028	$140.90	$140.90	$140.90
Purchase #4	$170.31	7.601%	$183.2553	$183.26	$183.25	$183.30
Purchase #5	$222.65	12.337%	$250.1183	$250.12	$250.10	$250.10
Purchase #6	$228.30	12.313%	$256.4106	$256.41	$256.40	$256.40
Purchase #7	$33.89	4.595%	$35.4472	$35.45	$35.45	$35.40
7 purchase totals =	$888.50		$987.3882	$987.39	$987.35	$987.40