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	$124.64	5.795%	$131.8629	$131.86	$131.85	$131.90
Purchase #2	$26.68	3.250%	$27.5471	$27.55	$27.55	$27.50
Purchase #3	$196.36	10.428%	$216.8364	$216.84	$216.85	$216.80
Purchase #4	$94.50	6.428%	$100.5745	$100.57	$100.55	$100.60
Purchase #5	$156.25	6.745%	$166.7891	$166.79	$166.80	$166.80
Purchase #6	$168.43	8.820%	$183.2855	$183.29	$183.30	$183.30
Purchase #7	$24.60	11.446%	$27.4157	$27.42	$27.40	$27.40
7 purchase totals =	$791.46		$854.3112	$854.32	$854.30	$854.30