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	$173.81	6.539%	$185.1754	$185.18	$185.20	$185.20
Purchase #2	$208.66	9.703%	$228.9063	$228.91	$228.90	$228.90
Purchase #3	$135.77	6.306%	$144.3317	$144.33	$144.35	$144.30
Purchase #4	$185.51	4.837%	$194.4831	$194.48	$194.50	$194.50
Purchase #5	$136.79	11.678%	$152.7643	$152.76	$152.75	$152.80
Purchase #6	$219.86	9.337%	$240.3883	$240.39	$240.40	$240.40
Purchase #7	$130.38	9.311%	$142.5197	$142.52	$142.50	$142.50
7 purchase totals =	$1,190.78		$1,288.5688	$1,288.57	$1,288.60	$1,288.60