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	$121.78	6.778%	$130.0342	$130.03	$130.05	$130.00
Purchase #2	$61.72	6.111%	$65.4917	$65.49	$65.50	$65.50
Purchase #3	$69.90	8.747%	$76.0142	$76.01	$76.00	$76.00
Purchase #4	$234.43	8.591%	$254.5699	$254.57	$254.55	$254.60
Purchase #5	$73.57	6.394%	$78.2741	$78.27	$78.25	$78.30
Purchase #6	$45.91	9.510%	$50.276	$50.28	$50.30	$50.30
Purchase #7	$17.26	9.588%	$18.9149	$18.91	$18.90	$18.90
7 purchase totals =	$624.57		$673.5750	$673.56	$673.55	$673.60