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	$94.40	11.792%	$105.5316	$105.53	$105.55	$105.50
Purchase #2	$63.31	13.279%	$71.7169	$71.72	$71.70	$71.70
Purchase #3	$202.88	5.641%	$214.3245	$214.32	$214.30	$214.30
Purchase #4	$96.86	10.588%	$107.1155	$107.12	$107.10	$107.10
Purchase #5	$95.90	7.313%	$102.9132	$102.91	$102.90	$102.90
Purchase #6	$72.54	8.535%	$78.7313	$78.73	$78.75	$78.70
Purchase #7	$16.27	7.629%	$17.5112	$17.51	$17.50	$17.50
7 purchase totals =	$642.16		$697.8442	$697.84	$697.80	$697.70