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	$184.36	13.127%	$208.5609	$208.56	$208.55	$208.60
Purchase #2	$194.28	3.256%	$200.6058	$200.61	$200.60	$200.60
Purchase #3	$134.86	5.229%	$141.9118	$141.91	$141.90	$141.90
Purchase #4	$223.26	12.118%	$250.3146	$250.31	$250.30	$250.30
Purchase #5	$113.29	13.873%	$129.0067	$129.01	$129.00	$129.00
Purchase #6	$192.84	13.510%	$218.8927	$218.89	$218.90	$218.90
Purchase #7	$51.68	4.158%	$53.8289	$53.83	$53.85	$53.80
7 purchase totals =	$1,094.57		$1,203.1214	$1,203.12	$1,203.10	$1,203.10