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	$68.33	6.200%	$72.5665	$72.57	$72.55	$72.60
Purchase #2	$93.80	11.162%	$104.27	$104.27	$104.25	$104.30
Purchase #3	$110.41	4.445%	$115.3177	$115.32	$115.30	$115.30
Purchase #4	$15.52	4.348%	$16.1948	$16.19	$16.20	$16.20
Purchase #5	$184.54	3.247%	$190.532	$190.53	$190.55	$190.50
Purchase #6	$123.38	6.673%	$131.6131	$131.61	$131.60	$131.60
Purchase #7	$208.46	6.207%	$221.3991	$221.40	$221.40	$221.40
7 purchase totals =	$804.44		$851.8932	$851.89	$851.85	$851.90