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	$10.93	3.799%	$11.3452	$11.35	$11.35	$11.30
Purchase #2	$192.47	12.127%	$215.8108	$215.81	$215.80	$215.80
Purchase #3	$99.98	6.304%	$106.2827	$106.28	$106.30	$106.30
Purchase #4	$56.95	4.589%	$59.5634	$59.56	$59.55	$59.60
Purchase #5	$97.31	4.530%	$101.7181	$101.72	$101.70	$101.70
Purchase #6	$176.82	12.278%	$198.53	$198.53	$198.55	$198.50
Purchase #7	$167.57	8.297%	$181.4733	$181.47	$181.45	$181.50
7 purchase totals =	$802.03		$874.7235	$874.72	$874.70	$874.70