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	$94.69	6.524%	$100.8676	$100.87	$100.85	$100.90
Purchase #2	$45.95	10.103%	$50.5923	$50.59	$50.60	$50.60
Purchase #3	$80.54	6.418%	$85.7091	$85.71	$85.70	$85.70
Purchase #4	$37.71	5.373%	$39.7362	$39.74	$39.75	$39.70
Purchase #5	$156.63	12.608%	$176.3779	$176.38	$176.40	$176.40
Purchase #6	$90.83	7.370%	$97.5242	$97.52	$97.50	$97.50
Purchase #7	$218.28	4.799%	$228.7553	$228.76	$228.75	$228.80
7 purchase totals =	$724.63		$779.5626	$779.57	$779.55	$779.60