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	$64.70	7.483%	$69.5415	$69.54	$69.55	$69.50
Purchase #2	$31.53	12.839%	$35.5781	$35.58	$35.60	$35.60
Purchase #3	$45.47	5.112%	$47.7944	$47.79	$47.80	$47.80
Purchase #4	$80.88	11.584%	$90.2491	$90.25	$90.25	$90.20
Purchase #5	$246.44	7.445%	$264.7875	$264.79	$264.80	$264.80
Purchase #6	$59.56	4.445%	$62.2074	$62.21	$62.20	$62.20
Purchase #7	$40.88	7.237%	$43.8385	$43.84	$43.85	$43.80
7 purchase totals =	$569.46		$613.9965	$614.00	$614.05	$613.90