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	$150.93	3.755%	$156.5974	$156.60	$156.60	$156.60
Purchase #2	$37.53	13.852%	$42.7287	$42.73	$42.75	$42.70
Purchase #3	$46.31	12.350%	$52.0293	$52.03	$52.05	$52.00
Purchase #4	$80.32	4.797%	$84.173	$84.17	$84.15	$84.20
Purchase #5	$12.50	7.858%	$13.4823	$13.48	$13.50	$13.50
Purchase #6	$53.93	9.478%	$59.0415	$59.04	$59.05	$59.00
Purchase #7	$202.69	8.289%	$219.491	$219.49	$219.50	$219.50
7 purchase totals =	$584.21		$627.5432	$627.54	$627.60	$627.50