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	$22.56	11.213%	$25.0897	$25.09	$25.10	$25.10
Purchase #2	$110.25	3.650%	$114.2741	$114.27	$114.25	$114.30
Purchase #3	$148.89	13.471%	$168.947	$168.95	$168.95	$168.90
Purchase #4	$203.85	10.392%	$225.0341	$225.03	$225.05	$225.00
Purchase #5	$50.81	9.752%	$55.765	$55.77	$55.75	$55.80
Purchase #6	$152.27	10.219%	$167.8305	$167.83	$167.85	$167.80
Purchase #7	$174.27	5.803%	$184.3829	$184.38	$184.40	$184.40
7 purchase totals =	$862.90		$941.3233	$941.32	$941.35	$941.30