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	$215.58	6.640%	$229.8945	$229.89	$229.90	$229.90
Purchase #2	$225.47	4.339%	$235.2531	$235.25	$235.25	$235.30
Purchase #3	$145.33	13.295%	$164.6516	$164.65	$164.65	$164.70
Purchase #4	$85.82	12.129%	$96.2291	$96.23	$96.25	$96.20
Purchase #5	$95.85	9.272%	$104.7372	$104.74	$104.75	$104.70
Purchase #6	$212.90	3.435%	$220.2131	$220.21	$220.20	$220.20
Purchase #7	$88.32	13.114%	$99.9023	$99.90	$99.90	$99.90
7 purchase totals =	$1,069.27		$1,150.8809	$1,150.87	$1,150.90	$1,150.90