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	$181.52	3.744%	$188.3161	$188.32	$188.30	$188.30
Purchase #2	$19.99	3.770%	$20.7436	$20.74	$20.75	$20.70
Purchase #3	$32.86	7.257%	$35.2447	$35.24	$35.25	$35.20
Purchase #4	$214.34	9.589%	$234.8931	$234.89	$234.90	$234.90
Purchase #5	$82.46	11.409%	$91.8679	$91.87	$91.85	$91.90
Purchase #6	$248.96	8.607%	$270.388	$270.39	$270.40	$270.40
Purchase #7	$223.55	13.395%	$253.4945	$253.49	$253.50	$253.50
7 purchase totals =	$1,003.68		$1,094.9479	$1,094.94	$1,094.95	$1,094.90