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	$166.95	5.629%	$176.3476	$176.35	$176.35	$176.30
Purchase #2	$98.35	11.191%	$109.3563	$109.36	$109.35	$109.40
Purchase #3	$110.74	5.669%	$117.0179	$117.02	$117.00	$117.00
Purchase #4	$165.34	12.377%	$185.8041	$185.80	$185.80	$185.80
Purchase #5	$166.89	4.171%	$173.851	$173.85	$173.85	$173.90
Purchase #6	$175.31	3.556%	$181.544	$181.54	$181.55	$181.50
Purchase #7	$136.40	13.351%	$154.6108	$154.61	$154.60	$154.60
7 purchase totals =	$1,019.98		$1,098.5317	$1,098.53	$1,098.50	$1,098.50