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	$97.73	3.104%	$100.7635	$100.76	$100.75	$100.80
Purchase #2	$47.75	7.614%	$51.3857	$51.39	$51.40	$51.40
Purchase #3	$110.30	8.523%	$119.7009	$119.70	$119.70	$119.70
Purchase #4	$55.50	13.222%	$62.8382	$62.84	$62.85	$62.80
Purchase #5	$211.38	6.727%	$225.5995	$225.60	$225.60	$225.60
Purchase #6	$98.40	11.170%	$109.3913	$109.39	$109.40	$109.40
Purchase #7	$207.63	4.284%	$216.5249	$216.52	$216.50	$216.50
7 purchase totals =	$828.69		$886.2040	$886.20	$886.20	$886.20