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	$209.74	4.261%	$218.677	$218.68	$218.70	$218.70
Purchase #2	$72.25	9.136%	$78.8508	$78.85	$78.85	$78.90
Purchase #3	$83.44	12.661%	$94.0043	$94.00	$94.00	$94.00
Purchase #4	$240.73	12.368%	$270.5035	$270.50	$270.50	$270.50
Purchase #5	$91.78	5.418%	$96.7526	$96.75	$96.75	$96.80
Purchase #6	$219.95	6.271%	$233.7431	$233.74	$233.75	$233.70
Purchase #7	$93.50	12.575%	$105.2576	$105.26	$105.25	$105.30
7 purchase totals =	$1,011.39		$1,097.7889	$1,097.78	$1,097.80	$1,097.90