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	$250.84	13.756%	$285.3456	$285.35	$285.35	$285.30
Purchase #2	$181.84	5.355%	$191.5775	$191.58	$191.60	$191.60
Purchase #3	$184.81	6.483%	$196.7912	$196.79	$196.80	$196.80
Purchase #4	$187.87	13.499%	$213.2306	$213.23	$213.25	$213.20
Purchase #5	$75.93	9.344%	$83.0249	$83.02	$83.00	$83.00
Purchase #6	$67.84	8.482%	$73.5942	$73.59	$73.60	$73.60
Purchase #7	$49.54	6.451%	$52.7358	$52.74	$52.75	$52.70
7 purchase totals =	$998.67		$1,096.2998	$1,096.30	$1,096.35	$1,096.20