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	$219.40	3.672%	$227.4564	$227.46	$227.45	$227.50
Purchase #2	$149.72	4.514%	$156.4784	$156.48	$156.50	$156.50
Purchase #3	$207.92	12.275%	$233.4422	$233.44	$233.45	$233.40
Purchase #4	$36.62	11.120%	$40.6921	$40.69	$40.70	$40.70
Purchase #5	$160.52	12.213%	$180.1243	$180.12	$180.10	$180.10
Purchase #6	$199.40	11.857%	$223.0429	$223.04	$223.05	$223.00
Purchase #7	$105.64	12.115%	$118.4383	$118.44	$118.45	$118.40
7 purchase totals =	$1,079.22		$1,179.6746	$1,179.67	$1,179.70	$1,179.60