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	$167.49	3.115%	$172.7073	$172.71	$172.70	$172.70
Purchase #2	$168.96	9.416%	$184.8693	$184.87	$184.85	$184.90
Purchase #3	$141.35	6.170%	$150.0713	$150.07	$150.05	$150.10
Purchase #4	$123.92	5.260%	$130.4382	$130.44	$130.45	$130.40
Purchase #5	$44.33	4.608%	$46.3727	$46.37	$46.35	$46.40
Purchase #6	$100.31	7.123%	$107.4551	$107.46	$107.45	$107.50
Purchase #7	$178.73	6.555%	$190.4458	$190.45	$190.45	$190.40
7 purchase totals =	$925.09		$982.3597	$982.37	$982.30	$982.40