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	$218.93	4.664%	$229.1409	$229.14	$229.15	$229.10
Purchase #2	$85.88	5.488%	$90.5931	$90.59	$90.60	$90.60
Purchase #3	$38.51	3.161%	$39.7273	$39.73	$39.75	$39.70
Purchase #4	$47.96	4.844%	$50.2832	$50.28	$50.30	$50.30
Purchase #5	$72.93	10.411%	$80.5227	$80.52	$80.50	$80.50
Purchase #6	$231.42	3.709%	$240.0034	$240.00	$240.00	$240.00
Purchase #7	$173.56	10.815%	$192.3305	$192.33	$192.35	$192.30
7 purchase totals =	$869.19		$922.6011	$922.59	$922.65	$922.50