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	$164.43	6.417%	$174.9815	$174.98	$175.00	$175.00
Purchase #2	$168.30	10.186%	$185.443	$185.44	$185.45	$185.40
Purchase #3	$154.81	6.297%	$164.5584	$164.56	$164.55	$164.60
Purchase #4	$145.81	4.157%	$151.8713	$151.87	$151.85	$151.90
Purchase #5	$198.84	10.619%	$219.9548	$219.95	$219.95	$220.00
Purchase #6	$73.42	8.801%	$79.8817	$79.88	$79.90	$79.90
Purchase #7	$79.67	6.682%	$84.9935	$84.99	$85.00	$85.00
7 purchase totals =	$985.28		$1,061.6842	$1,061.67	$1,061.70	$1,061.80