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	$108.44	10.298%	$119.6072	$119.61	$119.60	$119.60
Purchase #2	$183.72	10.121%	$202.3143	$202.31	$202.30	$202.30
Purchase #3	$56.36	11.482%	$62.8313	$62.83	$62.85	$62.80
Purchase #4	$127.76	13.146%	$144.5553	$144.56	$144.55	$144.60
Purchase #5	$89.49	7.855%	$96.5194	$96.52	$96.50	$96.50
Purchase #6	$205.59	10.725%	$227.6395	$227.64	$227.65	$227.60
Purchase #7	$175.45	8.445%	$190.2668	$190.27	$190.25	$190.30
7 purchase totals =	$946.81		$1,043.7338	$1,043.74	$1,043.70	$1,043.70