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	$203.45	7.580%	$218.8715	$218.87	$218.85	$218.90
Purchase #2	$80.74	6.675%	$86.1294	$86.13	$86.15	$86.10
Purchase #3	$213.47	6.659%	$227.685	$227.69	$227.70	$227.70
Purchase #4	$165.89	11.744%	$185.3721	$185.37	$185.35	$185.40
Purchase #5	$86.62	11.820%	$96.8585	$96.86	$96.85	$96.90
Purchase #6	$65.40	11.174%	$72.7078	$72.71	$72.70	$72.70
Purchase #7	$220.54	11.349%	$245.5691	$245.57	$245.55	$245.60
7 purchase totals =	$1,036.11		$1,133.1934	$1,133.20	$1,133.15	$1,133.30