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	$153.66	7.618%	$165.3658	$165.37	$165.35	$165.40
Purchase #2	$128.89	10.641%	$142.6052	$142.61	$142.60	$142.60
Purchase #3	$138.28	3.248%	$142.7713	$142.77	$142.75	$142.80
Purchase #4	$10.57	9.632%	$11.5881	$11.59	$11.60	$11.60
Purchase #5	$175.65	5.314%	$184.984	$184.98	$185.00	$185.00
Purchase #6	$173.97	4.562%	$181.9065	$181.91	$181.90	$181.90
Purchase #7	$54.71	6.317%	$58.166	$58.17	$58.15	$58.20
7 purchase totals =	$835.73		$887.3869	$887.40	$887.35	$887.50