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	$118.57	7.268%	$127.1877	$127.19	$127.20	$127.20
Purchase #2	$53.68	10.681%	$59.4136	$59.41	$59.40	$59.40
Purchase #3	$57.43	3.830%	$59.6296	$59.63	$59.65	$59.60
Purchase #4	$104.35	12.748%	$117.6525	$117.65	$117.65	$117.70
Purchase #5	$151.64	10.258%	$167.1952	$167.20	$167.20	$167.20
Purchase #6	$28.31	11.253%	$31.4957	$31.50	$31.50	$31.50
Purchase #7	$41.93	11.121%	$46.593	$46.59	$46.60	$46.60
7 purchase totals =	$555.91		$609.1673	$609.17	$609.20	$609.20