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	$233.78	9.843%	$256.791	$256.79	$256.80	$256.80
Purchase #2	$225.31	8.862%	$245.277	$245.28	$245.30	$245.30
Purchase #3	$63.68	11.776%	$71.179	$71.18	$71.20	$71.20
Purchase #4	$56.88	13.544%	$64.5838	$64.58	$64.60	$64.60
Purchase #5	$218.64	10.477%	$241.5469	$241.55	$241.55	$241.50
Purchase #6	$55.62	10.705%	$61.5741	$61.57	$61.55	$61.60
Purchase #7	$106.48	3.718%	$110.4389	$110.44	$110.45	$110.40
7 purchase totals =	$960.39		$1,051.3907	$1,051.39	$1,051.45	$1,051.40