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	$56.66	4.245%	$59.0652	$59.07	$59.05	$59.10
Purchase #2	$250.73	6.281%	$266.4784	$266.48	$266.50	$266.50
Purchase #3	$176.57	5.567%	$186.3997	$186.40	$186.40	$186.40
Purchase #4	$165.85	9.182%	$181.0783	$181.08	$181.10	$181.10
Purchase #5	$209.74	13.705%	$238.4849	$238.48	$238.50	$238.50
Purchase #6	$228.54	12.223%	$256.4744	$256.47	$256.45	$256.50
Purchase #7	$165.31	11.514%	$184.3438	$184.34	$184.35	$184.30
7 purchase totals =	$1,253.40		$1,372.3247	$1,372.32	$1,372.35	$1,372.40