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	$153.31	12.681%	$172.7512	$172.75	$172.75	$172.80
Purchase #2	$176.72	11.168%	$196.4561	$196.46	$196.45	$196.50
Purchase #3	$136.59	5.399%	$143.9645	$143.96	$143.95	$144.00
Purchase #4	$115.61	12.591%	$130.1665	$130.17	$130.15	$130.20
Purchase #5	$172.36	11.735%	$192.5864	$192.59	$192.60	$192.60
Purchase #6	$25.60	9.643%	$28.0686	$28.07	$28.05	$28.10
Purchase #7	$171.70	5.416%	$180.9993	$181.00	$181.00	$181.00
7 purchase totals =	$951.89		$1,044.9926	$1,045.00	$1,044.95	$1,045.20