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	$155.72	3.134%	$160.6003	$160.60	$160.60	$160.60
Purchase #2	$57.72	5.475%	$60.8802	$60.88	$60.90	$60.90
Purchase #3	$89.52	5.639%	$94.568	$94.57	$94.55	$94.60
Purchase #4	$197.33	13.304%	$223.5828	$223.58	$223.60	$223.60
Purchase #5	$17.72	3.192%	$18.2856	$18.29	$18.30	$18.30
Purchase #6	$46.85	4.197%	$48.8163	$48.82	$48.80	$48.80
Purchase #7	$168.31	11.674%	$187.9585	$187.96	$187.95	$188.00
7 purchase totals =	$733.17		$794.6917	$794.70	$794.70	$794.80