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	$85.38	7.281%	$91.5965	$91.60	$91.60	$91.60
Purchase #2	$205.43	7.653%	$221.1516	$221.15	$221.15	$221.20
Purchase #3	$161.36	7.519%	$173.4927	$173.49	$173.50	$173.50
Purchase #4	$65.73	7.819%	$70.8694	$70.87	$70.85	$70.90
Purchase #5	$98.32	11.758%	$109.8805	$109.88	$109.90	$109.90
Purchase #6	$192.29	12.639%	$216.5935	$216.59	$216.60	$216.60
Purchase #7	$185.79	6.172%	$197.257	$197.26	$197.25	$197.30
7 purchase totals =	$994.30		$1,080.8412	$1,080.84	$1,080.85	$1,081.00