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	$137.93	6.335%	$146.6679	$146.67	$146.65	$146.70
Purchase #2	$224.40	11.587%	$250.4012	$250.40	$250.40	$250.40
Purchase #3	$31.46	7.722%	$33.8893	$33.89	$33.90	$33.90
Purchase #4	$191.98	10.225%	$211.61	$211.61	$211.60	$211.60
Purchase #5	$128.81	4.137%	$134.1389	$134.14	$134.15	$134.10
Purchase #6	$99.35	4.760%	$104.0791	$104.08	$104.10	$104.10
Purchase #7	$123.91	3.199%	$127.8739	$127.87	$127.85	$127.90
7 purchase totals =	$937.84		$1,008.6603	$1,008.66	$1,008.65	$1,008.70