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	$124.49	7.437%	$133.7483	$133.75	$133.75	$133.70
Purchase #2	$55.40	5.404%	$58.3938	$58.39	$58.40	$58.40
Purchase #3	$209.45	4.841%	$219.5895	$219.59	$219.60	$219.60
Purchase #4	$81.41	9.709%	$89.3141	$89.31	$89.30	$89.30
Purchase #5	$225.87	4.114%	$235.1623	$235.16	$235.15	$235.20
Purchase #6	$192.63	7.204%	$206.5071	$206.51	$206.50	$206.50
Purchase #7	$103.90	5.778%	$109.9033	$109.90	$109.90	$109.90
7 purchase totals =	$993.15		$1,052.6184	$1,052.61	$1,052.60	$1,052.60