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	$82.90	13.577%	$94.1553	$94.16	$94.15	$94.20
Purchase #2	$59.66	10.709%	$66.049	$66.05	$66.05	$66.00
Purchase #3	$65.52	12.104%	$73.4505	$73.45	$73.45	$73.50
Purchase #4	$235.40	3.790%	$244.3217	$244.32	$244.30	$244.30
Purchase #5	$177.89	4.199%	$185.3596	$185.36	$185.35	$185.40
Purchase #6	$240.34	12.658%	$270.7622	$270.76	$270.75	$270.80
Purchase #7	$102.57	3.767%	$106.4338	$106.43	$106.45	$106.40
7 purchase totals =	$964.28		$1,040.5321	$1,040.53	$1,040.50	$1,040.60