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	$192.46	3.474%	$199.1461	$199.15	$199.15	$199.10
Purchase #2	$147.96	3.324%	$152.8782	$152.88	$152.90	$152.90
Purchase #3	$104.68	12.720%	$117.9953	$118.00	$118.00	$118.00
Purchase #4	$247.31	9.350%	$270.4335	$270.43	$270.45	$270.40
Purchase #5	$181.77	5.569%	$191.8928	$191.89	$191.90	$191.90
Purchase #6	$183.62	10.759%	$203.3757	$203.38	$203.40	$203.40
Purchase #7	$149.84	9.734%	$164.4254	$164.43	$164.45	$164.40
7 purchase totals =	$1,207.64		$1,300.1470	$1,300.16	$1,300.25	$1,300.10