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	$92.67	13.685%	$105.3519	$105.35	$105.35	$105.40
Purchase #2	$76.94	7.709%	$82.8713	$82.87	$82.85	$82.90
Purchase #3	$77.40	10.679%	$85.6655	$85.67	$85.65	$85.70
Purchase #4	$179.78	6.450%	$191.3758	$191.38	$191.40	$191.40
Purchase #5	$241.25	13.638%	$274.1517	$274.15	$274.15	$274.20
Purchase #6	$220.73	12.237%	$247.7407	$247.74	$247.75	$247.70
Purchase #7	$183.98	6.472%	$195.8872	$195.89	$195.90	$195.90
7 purchase totals =	$1,072.75		$1,183.0441	$1,183.05	$1,183.05	$1,183.20