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	$89.86	10.236%	$99.0581	$99.06	$99.05	$99.10
Purchase #2	$98.73	9.364%	$107.9751	$107.98	$108.00	$108.00
Purchase #3	$37.91	6.765%	$40.4746	$40.47	$40.45	$40.50
Purchase #4	$113.35	3.658%	$117.4963	$117.50	$117.50	$117.50
Purchase #5	$99.68	12.873%	$112.5118	$112.51	$112.50	$112.50
Purchase #6	$85.94	12.357%	$96.5596	$96.56	$96.55	$96.60
Purchase #7	$179.42	5.410%	$189.1266	$189.13	$189.15	$189.10
7 purchase totals =	$704.89		$763.2021	$763.21	$763.20	$763.30