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	$190.96	10.774%	$211.534	$211.53	$211.55	$211.50
Purchase #2	$161.55	12.234%	$181.314	$181.31	$181.30	$181.30
Purchase #3	$157.88	6.789%	$168.5985	$168.60	$168.60	$168.60
Purchase #4	$233.40	12.518%	$262.617	$262.62	$262.60	$262.60
Purchase #5	$102.36	6.267%	$108.7749	$108.77	$108.75	$108.80
Purchase #6	$196.92	10.787%	$218.1618	$218.16	$218.15	$218.20
Purchase #7	$102.45	5.740%	$108.3306	$108.33	$108.35	$108.30
7 purchase totals =	$1,145.52		$1,259.3308	$1,259.32	$1,259.30	$1,259.30