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	$172.41	7.568%	$185.458	$185.46	$185.45	$185.50
Purchase #2	$158.75	9.273%	$173.4709	$173.47	$173.45	$173.50
Purchase #3	$40.76	11.420%	$45.4148	$45.41	$45.40	$45.40
Purchase #4	$80.91	10.280%	$89.2275	$89.23	$89.25	$89.20
Purchase #5	$246.86	6.402%	$262.664	$262.66	$262.65	$262.70
Purchase #6	$167.73	11.131%	$186.4	$186.40	$186.40	$186.40
Purchase #7	$25.44	3.104%	$26.2297	$26.23	$26.25	$26.20
7 purchase totals =	$892.86		$968.8649	$968.86	$968.85	$968.90