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	$200.80	9.657%	$220.1913	$220.19	$220.20	$220.20
Purchase #2	$49.95	3.198%	$51.5474	$51.55	$51.55	$51.50
Purchase #3	$96.73	4.199%	$100.7917	$100.79	$100.80	$100.80
Purchase #4	$144.49	5.398%	$152.2896	$152.29	$152.30	$152.30
Purchase #5	$55.74	8.123%	$60.2678	$60.27	$60.25	$60.30
Purchase #6	$55.72	6.751%	$59.4817	$59.48	$59.50	$59.50
Purchase #7	$84.32	5.567%	$89.0141	$89.01	$89.00	$89.00
7 purchase totals =	$687.75		$733.5836	$733.58	$733.60	$733.60