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	$36.69	10.767%	$40.6404	$40.64	$40.65	$40.60
Purchase #2	$120.25	5.781%	$127.2017	$127.20	$127.20	$127.20
Purchase #3	$223.84	12.447%	$251.7014	$251.70	$251.70	$251.70
Purchase #4	$212.30	12.545%	$238.933	$238.93	$238.95	$238.90
Purchase #5	$241.25	12.284%	$270.8852	$270.89	$270.90	$270.90
Purchase #6	$54.48	8.826%	$59.2884	$59.29	$59.30	$59.30
Purchase #7	$33.93	3.656%	$35.1705	$35.17	$35.15	$35.20
7 purchase totals =	$922.74		$1,023.8206	$1,023.82	$1,023.85	$1,023.80