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	$142.56	5.848%	$150.8969	$150.90	$150.90	$150.90
Purchase #2	$12.35	5.784%	$13.0643	$13.06	$13.05	$13.10
Purchase #3	$229.72	5.349%	$242.0077	$242.01	$242.00	$242.00
Purchase #4	$85.25	11.824%	$95.33	$95.33	$95.35	$95.30
Purchase #5	$249.45	8.194%	$269.8899	$269.89	$269.90	$269.90
Purchase #6	$30.78	9.645%	$33.7487	$33.75	$33.75	$33.70
Purchase #7	$81.93	10.241%	$90.3205	$90.32	$90.30	$90.30
7 purchase totals =	$832.04		$895.2580	$895.26	$895.25	$895.20