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	$125.44	6.104%	$133.0969	$133.10	$133.10	$133.10
Purchase #2	$118.58	9.656%	$130.0301	$130.03	$130.05	$130.00
Purchase #3	$102.53	13.737%	$116.6145	$116.61	$116.60	$116.60
Purchase #4	$131.89	5.760%	$139.4869	$139.49	$139.50	$139.50
Purchase #5	$28.81	3.289%	$29.7576	$29.76	$29.75	$29.80
Purchase #6	$101.50	12.869%	$114.562	$114.56	$114.55	$114.60
Purchase #7	$38.78	5.451%	$40.8939	$40.89	$40.90	$40.90
7 purchase totals =	$647.53		$704.4419	$704.44	$704.45	$704.50