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	$218.52	7.271%	$234.4086	$234.41	$234.40	$234.40
Purchase #2	$103.52	5.741%	$109.4631	$109.46	$109.45	$109.50
Purchase #3	$57.92	12.474%	$65.1449	$65.14	$65.15	$65.10
Purchase #4	$73.93	5.388%	$77.9133	$77.91	$77.90	$77.90
Purchase #5	$192.89	9.846%	$211.8819	$211.88	$211.90	$211.90
Purchase #6	$232.46	5.765%	$245.8613	$245.86	$245.85	$245.90
Purchase #7	$36.61	9.497%	$40.0869	$40.09	$40.10	$40.10
7 purchase totals =	$915.85		$984.7600	$984.75	$984.75	$984.80