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	$131.43	4.701%	$137.6085	$137.61	$137.60	$137.60
Purchase #2	$30.87	4.557%	$32.2767	$32.28	$32.30	$32.30
Purchase #3	$152.92	10.374%	$168.7839	$168.78	$168.80	$168.80
Purchase #4	$144.94	10.623%	$160.337	$160.34	$160.35	$160.30
Purchase #5	$58.30	12.156%	$65.3869	$65.39	$65.40	$65.40
Purchase #6	$22.69	7.552%	$24.4035	$24.40	$24.40	$24.40
Purchase #7	$83.87	10.487%	$92.6654	$92.67	$92.65	$92.70
7 purchase totals =	$625.02		$681.4619	$681.47	$681.50	$681.50