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	$72.54	5.272%	$76.3643	$76.36	$76.35	$76.40
Purchase #2	$173.47	10.139%	$191.0581	$191.06	$191.05	$191.10
Purchase #3	$129.84	7.612%	$139.7234	$139.72	$139.70	$139.70
Purchase #4	$223.79	5.243%	$235.5233	$235.52	$235.50	$235.50
Purchase #5	$77.66	11.272%	$86.4138	$86.41	$86.40	$86.40
Purchase #6	$28.83	9.587%	$31.5939	$31.59	$31.60	$31.60
Purchase #7	$57.61	11.128%	$64.0208	$64.02	$64.00	$64.00
7 purchase totals =	$763.74		$824.6976	$824.68	$824.60	$824.70