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	$119.74	6.757%	$127.8308	$127.83	$127.85	$127.80
Purchase #2	$223.54	7.656%	$240.6542	$240.65	$240.65	$240.70
Purchase #3	$112.91	5.517%	$119.1392	$119.14	$119.15	$119.10
Purchase #4	$138.41	8.301%	$149.8994	$149.90	$149.90	$149.90
Purchase #5	$80.26	4.174%	$83.6101	$83.61	$83.60	$83.60
Purchase #6	$195.67	8.222%	$211.758	$211.76	$211.75	$211.80
Purchase #7	$114.47	7.578%	$123.1445	$123.14	$123.15	$123.10
7 purchase totals =	$985.00		$1,056.0362	$1,056.03	$1,056.05	$1,056.00