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	$243.52	10.478%	$269.036	$269.04	$269.05	$269.00
Purchase #2	$186.25	5.471%	$196.4397	$196.44	$196.45	$196.40
Purchase #3	$171.38	8.196%	$185.4263	$185.43	$185.45	$185.40
Purchase #4	$6.37	11.628%	$7.1107	$7.11	$7.10	$7.10
Purchase #5	$30.49	5.114%	$32.0493	$32.05	$32.05	$32.00
Purchase #6	$147.60	3.596%	$152.9077	$152.91	$152.90	$152.90
Purchase #7	$77.88	11.233%	$86.6283	$86.63	$86.65	$86.60
7 purchase totals =	$863.49		$929.5980	$929.61	$929.65	$929.40