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	$227.38	10.354%	$250.9229	$250.92	$250.90	$250.90
Purchase #2	$101.81	7.553%	$109.4997	$109.50	$109.50	$109.50
Purchase #3	$117.88	11.367%	$131.2794	$131.28	$131.30	$131.30
Purchase #4	$193.44	5.590%	$204.2533	$204.25	$204.25	$204.30
Purchase #5	$48.57	10.323%	$53.5839	$53.58	$53.60	$53.60
Purchase #6	$95.74	13.621%	$108.7807	$108.78	$108.80	$108.80
Purchase #7	$157.60	4.608%	$164.8622	$164.86	$164.85	$164.90
7 purchase totals =	$942.42		$1,023.1821	$1,023.17	$1,023.20	$1,023.30