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	$213.33	9.225%	$233.0097	$233.01	$233.00	$233.00
Purchase #2	$172.74	3.330%	$178.4922	$178.49	$178.50	$178.50
Purchase #3	$177.55	4.253%	$185.1012	$185.10	$185.10	$185.10
Purchase #4	$100.47	8.758%	$109.2692	$109.27	$109.25	$109.30
Purchase #5	$187.35	11.772%	$209.4048	$209.40	$209.40	$209.40
Purchase #6	$167.80	4.698%	$175.6832	$175.68	$175.70	$175.70
Purchase #7	$170.36	11.400%	$189.781	$189.78	$189.80	$189.80
7 purchase totals =	$1,189.60		$1,280.7413	$1,280.73	$1,280.75	$1,280.80