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	$40.56	11.249%	$45.1226	$45.12	$45.10	$45.10
Purchase #2	$89.37	3.808%	$92.7732	$92.77	$92.75	$92.80
Purchase #3	$53.74	3.722%	$55.7402	$55.74	$55.75	$55.70
Purchase #4	$51.39	11.699%	$57.4021	$57.40	$57.40	$57.40
Purchase #5	$126.49	12.468%	$142.2608	$142.26	$142.25	$142.30
Purchase #6	$94.89	6.224%	$100.796	$100.80	$100.80	$100.80
Purchase #7	$18.38	5.627%	$19.4142	$19.41	$19.40	$19.40
7 purchase totals =	$474.82		$513.5091	$513.50	$513.45	$513.50