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	$190.71	12.309%	$214.1845	$214.18	$214.20	$214.20
Purchase #2	$147.25	13.773%	$167.5307	$167.53	$167.55	$167.50
Purchase #3	$192.71	7.401%	$206.9725	$206.97	$206.95	$207.00
Purchase #4	$89.71	7.609%	$96.536	$96.54	$96.55	$96.50
Purchase #5	$150.55	7.728%	$162.1845	$162.18	$162.20	$162.20
Purchase #6	$231.74	4.631%	$242.4719	$242.47	$242.45	$242.50
Purchase #7	$18.39	5.804%	$19.4574	$19.46	$19.45	$19.50
7 purchase totals =	$1,021.06		$1,109.3375	$1,109.33	$1,109.35	$1,109.40