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	$190.92	11.700%	$213.2576	$213.26	$213.25	$213.30
Purchase #2	$73.71	6.379%	$78.412	$78.41	$78.40	$78.40
Purchase #3	$180.27	3.207%	$186.0513	$186.05	$186.05	$186.10
Purchase #4	$151.88	8.859%	$165.335	$165.34	$165.35	$165.30
Purchase #5	$211.72	6.629%	$225.7549	$225.75	$225.75	$225.80
Purchase #6	$48.39	7.166%	$51.8576	$51.86	$51.85	$51.90
Purchase #7	$67.35	13.184%	$76.2294	$76.23	$76.25	$76.20
7 purchase totals =	$924.24		$996.8978	$996.90	$996.90	$997.00