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	$85.85	13.545%	$97.4784	$97.48	$97.50	$97.50
Purchase #2	$53.80	6.760%	$57.4369	$57.44	$57.45	$57.40
Purchase #3	$174.27	6.254%	$185.1688	$185.17	$185.15	$185.20
Purchase #4	$57.67	5.666%	$60.9376	$60.94	$60.95	$60.90
Purchase #5	$87.88	13.117%	$99.4072	$99.41	$99.40	$99.40
Purchase #6	$204.25	8.803%	$222.2301	$222.23	$222.25	$222.20
Purchase #7	$187.57	12.596%	$211.1963	$211.20	$211.20	$211.20
7 purchase totals =	$851.29		$933.8553	$933.87	$933.90	$933.80