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	$130.62	10.565%	$144.42	$144.42	$144.40	$144.40
Purchase #2	$42.34	8.321%	$45.8631	$45.86	$45.85	$45.90
Purchase #3	$52.81	12.111%	$59.2058	$59.21	$59.20	$59.20
Purchase #4	$48.74	3.402%	$50.3981	$50.40	$50.40	$50.40
Purchase #5	$196.75	13.477%	$223.266	$223.27	$223.25	$223.30
Purchase #6	$92.73	11.159%	$103.0777	$103.08	$103.10	$103.10
Purchase #7	$25.98	6.350%	$27.6297	$27.63	$27.65	$27.60
7 purchase totals =	$589.97		$653.8604	$653.87	$653.85	$653.90