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	$75.87	10.462%	$83.8075	$83.81	$83.80	$83.80
Purchase #2	$226.54	3.185%	$233.7553	$233.76	$233.75	$233.80
Purchase #3	$39.27	9.110%	$42.8475	$42.85	$42.85	$42.80
Purchase #4	$226.71	12.206%	$254.3822	$254.38	$254.40	$254.40
Purchase #5	$228.91	10.668%	$253.3301	$253.33	$253.35	$253.30
Purchase #6	$58.77	7.162%	$62.9791	$62.98	$63.00	$63.00
Purchase #7	$136.62	4.221%	$142.3867	$142.39	$142.40	$142.40
7 purchase totals =	$992.69		$1,073.4884	$1,073.50	$1,073.55	$1,073.50