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	$88.55	12.777%	$99.864	$99.86	$99.85	$99.90
Purchase #2	$184.31	8.664%	$200.2786	$200.28	$200.30	$200.30
Purchase #3	$238.95	10.186%	$263.2894	$263.29	$263.30	$263.30
Purchase #4	$234.49	13.427%	$265.975	$265.98	$266.00	$266.00
Purchase #5	$35.90	4.872%	$37.649	$37.65	$37.65	$37.60
Purchase #6	$250.88	7.479%	$269.6433	$269.64	$269.65	$269.60
Purchase #7	$97.61	7.572%	$105.001	$105.00	$105.00	$105.00
7 purchase totals =	$1,130.69		$1,241.7003	$1,241.70	$1,241.75	$1,241.70