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	$173.98	9.524%	$190.5499	$190.55	$190.55	$190.50
Purchase #2	$24.82	3.267%	$25.6309	$25.63	$25.65	$25.60
Purchase #3	$42.25	9.759%	$46.3732	$46.37	$46.35	$46.40
Purchase #4	$36.29	5.370%	$38.2388	$38.24	$38.25	$38.20
Purchase #5	$84.41	5.230%	$88.8246	$88.82	$88.80	$88.80
Purchase #6	$154.67	3.781%	$160.5181	$160.52	$160.50	$160.50
Purchase #7	$64.40	11.663%	$71.911	$71.91	$71.90	$71.90
7 purchase totals =	$580.82		$622.0465	$622.04	$622.00	$621.90