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	$96.36	9.675%	$105.6828	$105.68	$105.70	$105.70
Purchase #2	$243.68	11.129%	$270.7991	$270.80	$270.80	$270.80
Purchase #3	$10.75	6.105%	$11.4063	$11.41	$11.40	$11.40
Purchase #4	$159.47	5.621%	$168.4338	$168.43	$168.45	$168.40
Purchase #5	$175.96	6.718%	$187.781	$187.78	$187.80	$187.80
Purchase #6	$79.79	12.793%	$89.9975	$90.00	$90.00	$90.00
Purchase #7	$227.33	12.111%	$254.8619	$254.86	$254.85	$254.90
7 purchase totals =	$993.34		$1,088.9624	$1,088.96	$1,089.00	$1,089.00