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	$200.88	4.786%	$210.4941	$210.49	$210.50	$210.50
Purchase #2	$206.25	13.735%	$234.5784	$234.58	$234.60	$234.60
Purchase #3	$80.39	12.765%	$90.6518	$90.65	$90.65	$90.70
Purchase #4	$61.31	5.173%	$64.4816	$64.48	$64.50	$64.50
Purchase #5	$211.46	13.251%	$239.4806	$239.48	$239.50	$239.50
Purchase #6	$35.75	4.850%	$37.4839	$37.48	$37.50	$37.50
Purchase #7	$177.49	3.142%	$183.0667	$183.07	$183.05	$183.10
7 purchase totals =	$973.53		$1,060.2371	$1,060.23	$1,060.30	$1,060.40