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	$85.71	11.306%	$95.4004	$95.40	$95.40	$95.40
Purchase #2	$82.55	9.758%	$90.6052	$90.61	$90.60	$90.60
Purchase #3	$67.47	5.348%	$71.0783	$71.08	$71.10	$71.10
Purchase #4	$89.88	7.627%	$96.7351	$96.74	$96.75	$96.70
Purchase #5	$93.31	11.272%	$103.8279	$103.83	$103.85	$103.80
Purchase #6	$238.33	7.552%	$256.3287	$256.33	$256.35	$256.30
Purchase #7	$240.66	7.654%	$259.0801	$259.08	$259.10	$259.10
7 purchase totals =	$897.91		$973.0557	$973.07	$973.15	$973.00