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	$61.27	10.463%	$67.6807	$67.68	$67.70	$67.70
Purchase #2	$85.60	9.272%	$93.5368	$93.54	$93.55	$93.50
Purchase #3	$247.59	7.280%	$265.6146	$265.61	$265.60	$265.60
Purchase #4	$205.78	13.620%	$233.8072	$233.81	$233.80	$233.80
Purchase #5	$204.62	3.769%	$212.3321	$212.33	$212.35	$212.30
Purchase #6	$242.29	10.401%	$267.4906	$267.49	$267.50	$267.50
Purchase #7	$149.88	12.397%	$168.4606	$168.46	$168.45	$168.50
7 purchase totals =	$1,197.03		$1,308.9226	$1,308.92	$1,308.95	$1,308.90