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	$131.61	4.343%	$137.3258	$137.33	$137.35	$137.30
Purchase #2	$188.97	13.827%	$215.0989	$215.10	$215.10	$215.10
Purchase #3	$13.76	7.281%	$14.7619	$14.76	$14.75	$14.80
Purchase #4	$31.84	5.775%	$33.6788	$33.68	$33.70	$33.70
Purchase #5	$52.70	5.207%	$55.4441	$55.44	$55.45	$55.40
Purchase #6	$99.28	6.267%	$105.5019	$105.50	$105.50	$105.50
Purchase #7	$150.34	13.786%	$171.0659	$171.07	$171.05	$171.10
7 purchase totals =	$668.50		$732.8773	$732.88	$732.90	$732.90