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	$91.78	11.854%	$102.6596	$102.66	$102.65	$102.70
Purchase #2	$223.33	13.507%	$253.4952	$253.50	$253.50	$253.50
Purchase #3	$219.64	12.604%	$247.3234	$247.32	$247.30	$247.30
Purchase #4	$134.72	13.462%	$152.856	$152.86	$152.85	$152.90
Purchase #5	$86.75	4.172%	$90.3692	$90.37	$90.35	$90.40
Purchase #6	$44.92	8.191%	$48.5994	$48.60	$48.60	$48.60
Purchase #7	$197.89	4.465%	$206.7258	$206.73	$206.75	$206.70
7 purchase totals =	$999.03		$1,102.0286	$1,102.04	$1,102.00	$1,102.10