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	$211.41	5.268%	$222.5471	$222.55	$222.55	$222.50
Purchase #2	$61.64	6.770%	$65.813	$65.81	$65.80	$65.80
Purchase #3	$38.83	10.652%	$42.9662	$42.97	$42.95	$43.00
Purchase #4	$240.39	3.586%	$249.0104	$249.01	$249.00	$249.00
Purchase #5	$220.67	13.618%	$250.7208	$250.72	$250.70	$250.70
Purchase #6	$185.35	11.550%	$206.7579	$206.76	$206.75	$206.80
Purchase #7	$125.89	6.322%	$133.8488	$133.85	$133.85	$133.80
7 purchase totals =	$1,084.18		$1,171.6642	$1,171.67	$1,171.60	$1,171.60