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	$104.68	4.697%	$109.5968	$109.60	$109.60	$109.60
Purchase #2	$119.55	10.115%	$131.6425	$131.64	$131.65	$131.60
Purchase #3	$170.39	6.515%	$181.4909	$181.49	$181.50	$181.50
Purchase #4	$80.58	12.801%	$90.895	$90.90	$90.90	$90.90
Purchase #5	$35.89	13.227%	$40.6372	$40.64	$40.65	$40.60
Purchase #6	$52.58	8.369%	$56.9804	$56.98	$57.00	$57.00
Purchase #7	$127.63	5.463%	$134.6024	$134.60	$134.60	$134.60
7 purchase totals =	$691.30		$745.8452	$745.85	$745.90	$745.80