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	$160.37	4.534%	$167.6412	$167.64	$167.65	$167.60
Purchase #2	$28.77	6.144%	$30.5376	$30.54	$30.55	$30.50
Purchase #3	$35.61	6.561%	$37.9464	$37.95	$37.95	$37.90
Purchase #4	$85.93	6.401%	$91.4304	$91.43	$91.45	$91.40
Purchase #5	$188.93	9.632%	$207.1277	$207.13	$207.15	$207.10
Purchase #6	$54.51	9.376%	$59.6209	$59.62	$59.60	$59.60
Purchase #7	$174.97	3.212%	$180.59	$180.59	$180.60	$180.60
7 purchase totals =	$729.09		$774.8942	$774.90	$774.95	$774.70