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	$75.28	9.708%	$82.5882	$82.59	$82.60	$82.60
Purchase #2	$248.45	13.290%	$281.469	$281.47	$281.45	$281.50
Purchase #3	$160.39	8.467%	$173.9702	$173.97	$173.95	$174.00
Purchase #4	$20.25	8.705%	$22.0128	$22.01	$22.00	$22.00
Purchase #5	$210.40	5.556%	$222.0898	$222.09	$222.10	$222.10
Purchase #6	$57.41	11.736%	$64.1476	$64.15	$64.15	$64.10
Purchase #7	$173.28	12.114%	$194.2711	$194.27	$194.25	$194.30
7 purchase totals =	$945.46		$1,040.5487	$1,040.55	$1,040.50	$1,040.60