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	$57.58	6.604%	$61.3826	$61.38	$61.40	$61.40
Purchase #2	$198.29	13.561%	$225.1801	$225.18	$225.20	$225.20
Purchase #3	$205.88	6.815%	$219.9107	$219.91	$219.90	$219.90
Purchase #4	$59.67	8.231%	$64.5814	$64.58	$64.60	$64.60
Purchase #5	$238.88	13.419%	$270.9353	$270.94	$270.95	$270.90
Purchase #6	$45.41	8.506%	$49.2726	$49.27	$49.25	$49.30
Purchase #7	$148.39	8.132%	$160.4571	$160.46	$160.45	$160.50
7 purchase totals =	$954.10		$1,051.7198	$1,051.72	$1,051.75	$1,051.80