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	$63.68	6.265%	$67.6696	$67.67	$67.65	$67.70
Purchase #2	$139.27	6.116%	$147.7878	$147.79	$147.80	$147.80
Purchase #3	$69.87	12.144%	$78.355	$78.36	$78.35	$78.40
Purchase #4	$194.53	7.674%	$209.4582	$209.46	$209.45	$209.50
Purchase #5	$118.91	8.303%	$128.7831	$128.78	$128.80	$128.80
Purchase #6	$213.27	11.301%	$237.3716	$237.37	$237.35	$237.40
Purchase #7	$47.78	13.645%	$54.2996	$54.30	$54.30	$54.30
7 purchase totals =	$847.31		$923.7249	$923.73	$923.70	$923.90