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	$147.38	3.501%	$152.5398	$152.54	$152.55	$152.50
Purchase #2	$45.84	11.525%	$51.1231	$51.12	$51.10	$51.10
Purchase #3	$245.55	10.772%	$272.0006	$272.00	$272.00	$272.00
Purchase #4	$90.79	7.319%	$97.4349	$97.43	$97.45	$97.40
Purchase #5	$53.56	11.585%	$59.7649	$59.76	$59.75	$59.80
Purchase #6	$130.44	9.124%	$142.3413	$142.34	$142.35	$142.30
Purchase #7	$114.81	6.509%	$122.283	$122.28	$122.30	$122.30
7 purchase totals =	$828.37		$897.4876	$897.47	$897.50	$897.40