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	$69.71	12.826%	$78.651	$78.65	$78.65	$78.70
Purchase #2	$55.88	11.746%	$62.4437	$62.44	$62.45	$62.40
Purchase #3	$156.65	7.628%	$168.5993	$168.60	$168.60	$168.60
Purchase #4	$218.29	11.447%	$243.2777	$243.28	$243.30	$243.30
Purchase #5	$196.89	6.614%	$209.9123	$209.91	$209.90	$209.90
Purchase #6	$35.25	11.318%	$39.2396	$39.24	$39.25	$39.20
Purchase #7	$138.76	4.617%	$145.1665	$145.17	$145.15	$145.20
7 purchase totals =	$871.43		$947.2901	$947.29	$947.30	$947.30