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	$101.83	12.727%	$114.7899	$114.79	$114.80	$114.80
Purchase #2	$113.79	12.219%	$127.694	$127.69	$127.70	$127.70
Purchase #3	$52.37	6.758%	$55.9092	$55.91	$55.90	$55.90
Purchase #4	$157.26	6.383%	$167.2979	$167.30	$167.30	$167.30
Purchase #5	$160.86	10.743%	$178.1412	$178.14	$178.15	$178.10
Purchase #6	$129.98	5.865%	$137.6033	$137.60	$137.60	$137.60
Purchase #7	$141.51	10.497%	$156.3643	$156.36	$156.35	$156.40
7 purchase totals =	$857.60		$937.7998	$937.79	$937.80	$937.80