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	$67.65	5.685%	$71.4959	$71.50	$71.50	$71.50
Purchase #2	$201.89	10.237%	$222.5575	$222.56	$222.55	$222.60
Purchase #3	$117.50	8.714%	$127.739	$127.74	$127.75	$127.70
Purchase #4	$93.37	6.570%	$99.5044	$99.50	$99.50	$99.50
Purchase #5	$179.93	6.636%	$191.8702	$191.87	$191.85	$191.90
Purchase #6	$232.91	13.639%	$264.6766	$264.68	$264.70	$264.70
Purchase #7	$130.36	10.265%	$143.7415	$143.74	$143.75	$143.70
7 purchase totals =	$1,023.61		$1,121.5851	$1,121.59	$1,121.60	$1,121.60