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	$212.71	13.856%	$242.1831	$242.18	$242.20	$242.20
Purchase #2	$109.36	13.250%	$123.8502	$123.85	$123.85	$123.90
Purchase #3	$86.96	3.688%	$90.1671	$90.17	$90.15	$90.20
Purchase #4	$213.91	6.309%	$227.4056	$227.41	$227.40	$227.40
Purchase #5	$193.47	7.165%	$207.3321	$207.33	$207.35	$207.30
Purchase #6	$35.93	3.789%	$37.2914	$37.29	$37.30	$37.30
Purchase #7	$192.33	8.719%	$209.0993	$209.10	$209.10	$209.10
7 purchase totals =	$1,044.67		$1,137.3288	$1,137.33	$1,137.35	$1,137.40