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	$6.70	9.209%	$7.317	$7.32	$7.30	$7.30
Purchase #2	$106.28	3.271%	$109.7564	$109.76	$109.75	$109.80
Purchase #3	$207.64	8.613%	$225.524	$225.52	$225.50	$225.50
Purchase #4	$227.95	6.825%	$243.5076	$243.51	$243.50	$243.50
Purchase #5	$174.32	9.870%	$191.5254	$191.53	$191.55	$191.50
Purchase #6	$207.42	10.773%	$229.7654	$229.77	$229.75	$229.80
Purchase #7	$69.63	11.560%	$77.6792	$77.68	$77.70	$77.70
7 purchase totals =	$999.94		$1,085.0750	$1,085.09	$1,085.05	$1,085.10