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	$77.46	8.752%	$84.2393	$84.24	$84.25	$84.20
Purchase #2	$206.45	12.870%	$233.0201	$233.02	$233.00	$233.00
Purchase #3	$198.77	12.521%	$223.658	$223.66	$223.65	$223.70
Purchase #4	$101.62	10.542%	$112.3328	$112.33	$112.35	$112.30
Purchase #5	$162.74	3.164%	$167.8891	$167.89	$167.90	$167.90
Purchase #6	$85.72	11.214%	$95.3326	$95.33	$95.35	$95.30
Purchase #7	$161.42	11.706%	$180.3158	$180.32	$180.30	$180.30
7 purchase totals =	$994.18		$1,096.7877	$1,096.79	$1,096.80	$1,096.70