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	$109.88	5.366%	$115.7762	$115.78	$115.80	$115.80
Purchase #2	$71.99	8.673%	$78.2337	$78.23	$78.25	$78.20
Purchase #3	$194.67	5.106%	$204.6099	$204.61	$204.60	$204.60
Purchase #4	$162.68	10.870%	$180.3633	$180.36	$180.35	$180.40
Purchase #5	$64.86	4.635%	$67.8663	$67.87	$67.85	$67.90
Purchase #6	$162.61	10.169%	$179.1458	$179.15	$179.15	$179.10
Purchase #7	$118.62	7.397%	$127.3943	$127.39	$127.40	$127.40
7 purchase totals =	$885.31		$953.3895	$953.39	$953.40	$953.40