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	$179.46	4.454%	$187.4531	$187.45	$187.45	$187.50
Purchase #2	$92.40	4.802%	$96.837	$96.84	$96.85	$96.80
Purchase #3	$242.95	3.278%	$250.9139	$250.91	$250.90	$250.90
Purchase #4	$12.61	4.752%	$13.2092	$13.21	$13.20	$13.20
Purchase #5	$12.57	5.142%	$13.2163	$13.22	$13.20	$13.20
Purchase #6	$214.86	13.486%	$243.836	$243.84	$243.85	$243.80
Purchase #7	$157.75	4.221%	$164.4086	$164.41	$164.40	$164.40
7 purchase totals =	$912.60		$969.8741	$969.88	$969.85	$969.80