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	$222.27	7.422%	$238.7669	$238.77	$238.75	$238.80
Purchase #2	$94.83	9.402%	$103.7459	$103.75	$103.75	$103.70
Purchase #3	$31.80	4.754%	$33.3118	$33.31	$33.30	$33.30
Purchase #4	$66.80	6.505%	$71.1453	$71.15	$71.15	$71.10
Purchase #5	$197.52	10.408%	$218.0779	$218.08	$218.10	$218.10
Purchase #6	$87.96	3.430%	$90.977	$90.98	$91.00	$91.00
Purchase #7	$72.90	7.266%	$78.1969	$78.20	$78.20	$78.20
7 purchase totals =	$774.08		$834.2217	$834.24	$834.25	$834.20