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	$83.72	9.316%	$91.5194	$91.52	$91.50	$91.50
Purchase #2	$42.72	6.597%	$45.5382	$45.54	$45.55	$45.50
Purchase #3	$206.54	4.295%	$215.4109	$215.41	$215.40	$215.40
Purchase #4	$40.89	6.691%	$43.6259	$43.63	$43.65	$43.60
Purchase #5	$151.34	7.207%	$162.2471	$162.25	$162.25	$162.20
Purchase #6	$181.99	3.770%	$188.851	$188.85	$188.85	$188.90
Purchase #7	$215.85	10.196%	$237.8581	$237.86	$237.85	$237.90
7 purchase totals =	$923.05		$985.0506	$985.06	$985.05	$985.00