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	$93.82	7.412%	$100.7739	$100.77	$100.75	$100.80
Purchase #2	$237.73	6.790%	$253.8719	$253.87	$253.85	$253.90
Purchase #3	$119.98	9.678%	$131.5917	$131.59	$131.60	$131.60
Purchase #4	$128.98	6.716%	$137.6423	$137.64	$137.65	$137.60
Purchase #5	$169.44	8.550%	$183.9271	$183.93	$183.95	$183.90
Purchase #6	$203.88	5.669%	$215.438	$215.44	$215.45	$215.40
Purchase #7	$48.67	11.791%	$54.4087	$54.41	$54.40	$54.40
7 purchase totals =	$1,002.50		$1,077.6536	$1,077.65	$1,077.65	$1,077.60