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	$52.51	12.785%	$59.2234	$59.22	$59.20	$59.20
Purchase #2	$16.31	7.669%	$17.5608	$17.56	$17.55	$17.60
Purchase #3	$190.75	7.617%	$205.2794	$205.28	$205.30	$205.30
Purchase #4	$192.98	13.179%	$218.4128	$218.41	$218.40	$218.40
Purchase #5	$166.71	5.173%	$175.3339	$175.33	$175.35	$175.30
Purchase #6	$172.76	13.804%	$196.6078	$196.61	$196.60	$196.60
Purchase #7	$55.56	6.185%	$58.9964	$59.00	$59.00	$59.00
7 purchase totals =	$847.58		$931.4145	$931.41	$931.40	$931.40