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	$170.97	6.413%	$181.9343	$181.93	$181.95	$181.90
Purchase #2	$227.67	3.612%	$235.8934	$235.89	$235.90	$235.90
Purchase #3	$245.84	4.495%	$256.8905	$256.89	$256.90	$256.90
Purchase #4	$98.28	6.796%	$104.9591	$104.96	$104.95	$105.00
Purchase #5	$146.95	10.317%	$162.1108	$162.11	$162.10	$162.10
Purchase #6	$155.36	9.330%	$169.8551	$169.86	$169.85	$169.90
Purchase #7	$36.79	5.633%	$38.8624	$38.86	$38.85	$38.90
7 purchase totals =	$1,081.86		$1,150.5056	$1,150.50	$1,150.50	$1,150.60