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	$201.79	11.742%	$225.4842	$225.48	$225.50	$225.50
Purchase #2	$100.60	9.649%	$110.3069	$110.31	$110.30	$110.30
Purchase #3	$162.57	6.797%	$173.6199	$173.62	$173.60	$173.60
Purchase #4	$145.71	3.404%	$150.67	$150.67	$150.65	$150.70
Purchase #5	$154.39	9.322%	$168.7822	$168.78	$168.80	$168.80
Purchase #6	$122.86	4.104%	$127.9022	$127.90	$127.90	$127.90
Purchase #7	$127.56	3.704%	$132.2848	$132.28	$132.30	$132.30
7 purchase totals =	$1,015.48		$1,089.0502	$1,089.04	$1,089.05	$1,089.10