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	$193.30	7.658%	$208.1029	$208.10	$208.10	$208.10
Purchase #2	$214.34	6.141%	$227.5026	$227.50	$227.50	$227.50
Purchase #3	$146.74	12.461%	$165.0253	$165.03	$165.05	$165.00
Purchase #4	$142.88	9.537%	$156.5065	$156.51	$156.50	$156.50
Purchase #5	$85.83	6.152%	$91.1103	$91.11	$91.10	$91.10
Purchase #6	$103.80	6.288%	$110.3269	$110.33	$110.35	$110.30
Purchase #7	$77.89	13.380%	$88.3117	$88.31	$88.30	$88.30
7 purchase totals =	$964.78		$1,046.8862	$1,046.89	$1,046.90	$1,046.80