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	$224.31	9.769%	$246.2228	$246.22	$246.20	$246.20
Purchase #2	$104.83	7.315%	$112.4983	$112.50	$112.50	$112.50
Purchase #3	$140.50	11.251%	$156.3077	$156.31	$156.30	$156.30
Purchase #4	$158.74	5.848%	$168.0231	$168.02	$168.00	$168.00
Purchase #5	$74.43	7.723%	$80.1782	$80.18	$80.20	$80.20
Purchase #6	$100.56	6.820%	$107.4182	$107.42	$107.40	$107.40
Purchase #7	$170.72	11.695%	$190.6857	$190.69	$190.70	$190.70
7 purchase totals =	$974.09		$1,061.3340	$1,061.34	$1,061.30	$1,061.30