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	$72.39	13.246%	$81.9788	$81.98	$82.00	$82.00
Purchase #2	$169.89	8.252%	$183.9093	$183.91	$183.90	$183.90
Purchase #3	$46.59	8.298%	$50.456	$50.46	$50.45	$50.50
Purchase #4	$123.46	7.637%	$132.8886	$132.89	$132.90	$132.90
Purchase #5	$165.62	12.223%	$185.8637	$185.86	$185.85	$185.90
Purchase #6	$39.67	8.356%	$42.9848	$42.98	$43.00	$43.00
Purchase #7	$226.92	9.412%	$248.2777	$248.28	$248.30	$248.30
7 purchase totals =	$844.54		$926.3589	$926.36	$926.40	$926.50