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	$153.37	9.468%	$167.8911	$167.89	$167.90	$167.90
Purchase #2	$9.76	11.613%	$10.8934	$10.89	$10.90	$10.90
Purchase #3	$97.41	8.477%	$105.6674	$105.67	$105.65	$105.70
Purchase #4	$210.25	9.188%	$229.5678	$229.57	$229.55	$229.60
Purchase #5	$40.62	4.743%	$42.5466	$42.55	$42.55	$42.50
Purchase #6	$95.56	9.673%	$104.8035	$104.80	$104.80	$104.80
Purchase #7	$99.54	10.534%	$110.0255	$110.03	$110.05	$110.00
7 purchase totals =	$706.51		$771.3953	$771.40	$771.40	$771.40