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	$150.36	8.155%	$162.6219	$162.62	$162.60	$162.60
Purchase #2	$223.25	4.223%	$232.6778	$232.68	$232.70	$232.70
Purchase #3	$179.67	8.356%	$194.6832	$194.68	$194.70	$194.70
Purchase #4	$168.89	12.754%	$190.4302	$190.43	$190.45	$190.40
Purchase #5	$149.59	4.208%	$155.8847	$155.88	$155.90	$155.90
Purchase #6	$142.51	5.530%	$150.3908	$150.39	$150.40	$150.40
Purchase #7	$102.76	6.617%	$109.5596	$109.56	$109.55	$109.60
7 purchase totals =	$1,117.03		$1,196.2482	$1,196.24	$1,196.30	$1,196.30