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	$66.57	3.305%	$68.7701	$68.77	$68.75	$68.80
Purchase #2	$40.71	12.695%	$45.8781	$45.88	$45.90	$45.90
Purchase #3	$175.68	5.777%	$185.829	$185.83	$185.85	$185.80
Purchase #4	$61.60	4.478%	$64.3584	$64.36	$64.35	$64.40
Purchase #5	$232.56	13.561%	$264.0975	$264.10	$264.10	$264.10
Purchase #6	$57.72	5.102%	$60.6649	$60.66	$60.65	$60.70
Purchase #7	$211.85	8.314%	$229.4632	$229.46	$229.45	$229.50
7 purchase totals =	$846.69		$919.0612	$919.06	$919.05	$919.20