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	$135.95	4.384%	$141.91	$141.91	$141.90	$141.90
Purchase #2	$78.53	5.496%	$82.846	$82.85	$82.85	$82.80
Purchase #3	$10.72	8.861%	$11.6699	$11.67	$11.65	$11.70
Purchase #4	$53.64	5.822%	$56.7629	$56.76	$56.75	$56.80
Purchase #5	$75.27	3.675%	$78.0362	$78.04	$78.05	$78.00
Purchase #6	$101.97	3.513%	$105.5522	$105.55	$105.55	$105.60
Purchase #7	$155.26	8.389%	$168.2848	$168.28	$168.30	$168.30
7 purchase totals =	$611.34		$645.0620	$645.06	$645.05	$645.10