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	$224.39	8.415%	$243.2724	$243.27	$243.25	$243.30
Purchase #2	$218.49	8.790%	$237.6953	$237.70	$237.70	$237.70
Purchase #3	$225.62	13.342%	$255.7222	$255.72	$255.70	$255.70
Purchase #4	$124.87	11.720%	$139.5048	$139.50	$139.50	$139.50
Purchase #5	$77.49	6.482%	$82.5129	$82.51	$82.50	$82.50
Purchase #6	$83.86	12.571%	$94.402	$94.40	$94.40	$94.40
Purchase #7	$26.49	7.413%	$28.4537	$28.45	$28.45	$28.50
7 purchase totals =	$981.21		$1,081.5633	$1,081.55	$1,081.50	$1,081.60