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	$49.97	5.814%	$52.8753	$52.88	$52.90	$52.90
Purchase #2	$166.77	5.520%	$175.9757	$175.98	$176.00	$176.00
Purchase #3	$147.98	3.201%	$152.7168	$152.72	$152.70	$152.70
Purchase #4	$223.93	8.284%	$242.4804	$242.48	$242.50	$242.50
Purchase #5	$165.59	11.391%	$184.4524	$184.45	$184.45	$184.50
Purchase #6	$82.39	5.268%	$86.7303	$86.73	$86.75	$86.70
Purchase #7	$146.80	13.108%	$166.0425	$166.04	$166.05	$166.00
7 purchase totals =	$983.43		$1,061.2734	$1,061.28	$1,061.35	$1,061.30