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	$55.41	5.715%	$58.5767	$58.58	$58.60	$58.60
Purchase #2	$85.58	4.104%	$89.0922	$89.09	$89.10	$89.10
Purchase #3	$196.49	13.352%	$222.7253	$222.73	$222.75	$222.70
Purchase #4	$225.35	3.397%	$233.0051	$233.01	$233.00	$233.00
Purchase #5	$174.56	7.579%	$187.7899	$187.79	$187.80	$187.80
Purchase #6	$180.28	5.414%	$190.0404	$190.04	$190.05	$190.00
Purchase #7	$42.26	8.106%	$45.6856	$45.69	$45.70	$45.70
7 purchase totals =	$959.93		$1,026.9152	$1,026.93	$1,027.00	$1,026.90