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	$194.39	7.260%	$208.5027	$208.50	$208.50	$208.50
Purchase #2	$76.64	11.505%	$85.4574	$85.46	$85.45	$85.50
Purchase #3	$137.52	8.649%	$149.4141	$149.41	$149.40	$149.40
Purchase #4	$98.71	7.653%	$106.2643	$106.26	$106.25	$106.30
Purchase #5	$142.30	10.253%	$156.89	$156.89	$156.90	$156.90
Purchase #6	$89.75	5.662%	$94.8316	$94.83	$94.85	$94.80
Purchase #7	$87.61	5.396%	$92.3374	$92.34	$92.35	$92.30
7 purchase totals =	$826.92		$893.6975	$893.69	$893.70	$893.70