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	$95.37	5.343%	$100.4656	$100.47	$100.45	$100.50
Purchase #2	$144.65	8.164%	$156.4592	$156.46	$156.45	$156.50
Purchase #3	$222.75	3.201%	$229.8802	$229.88	$229.90	$229.90
Purchase #4	$114.39	9.515%	$125.2742	$125.27	$125.25	$125.30
Purchase #5	$108.85	10.497%	$120.276	$120.28	$120.30	$120.30
Purchase #6	$185.49	3.435%	$191.8616	$191.86	$191.85	$191.90
Purchase #7	$183.40	13.386%	$207.9499	$207.95	$207.95	$207.90
7 purchase totals =	$1,054.90		$1,132.1667	$1,132.17	$1,132.15	$1,132.30