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	$90.90	4.739%	$95.2078	$95.21	$95.20	$95.20
Purchase #2	$182.49	12.282%	$204.9034	$204.90	$204.90	$204.90
Purchase #3	$130.85	12.681%	$147.4431	$147.44	$147.45	$147.40
Purchase #4	$46.87	5.467%	$49.4324	$49.43	$49.45	$49.40
Purchase #5	$242.60	4.674%	$253.9391	$253.94	$253.95	$253.90
Purchase #6	$123.73	3.231%	$127.7277	$127.73	$127.75	$127.70
Purchase #7	$209.39	11.168%	$232.7747	$232.77	$232.75	$232.80
7 purchase totals =	$1,026.83		$1,111.4282	$1,111.42	$1,111.45	$1,111.30