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	$81.49	6.608%	$86.8749	$86.87	$86.85	$86.90
Purchase #2	$174.95	5.118%	$183.9039	$183.90	$183.90	$183.90
Purchase #3	$85.46	4.769%	$89.5356	$89.54	$89.55	$89.50
Purchase #4	$82.71	9.687%	$90.7221	$90.72	$90.70	$90.70
Purchase #5	$196.44	7.260%	$210.7015	$210.70	$210.70	$210.70
Purchase #6	$109.33	12.642%	$123.1515	$123.15	$123.15	$123.20
Purchase #7	$150.91	12.514%	$169.7949	$169.79	$169.80	$169.80
7 purchase totals =	$881.29		$954.6844	$954.67	$954.65	$954.70