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	$79.51	4.521%	$83.1046	$83.10	$83.10	$83.10
Purchase #2	$11.96	9.508%	$13.0972	$13.10	$13.10	$13.10
Purchase #3	$98.25	7.459%	$105.5785	$105.58	$105.60	$105.60
Purchase #4	$103.43	8.607%	$112.3322	$112.33	$112.35	$112.30
Purchase #5	$76.89	6.356%	$81.7771	$81.78	$81.80	$81.80
Purchase #6	$217.56	7.149%	$233.1134	$233.11	$233.10	$233.10
Purchase #7	$59.82	9.592%	$65.5579	$65.56	$65.55	$65.60
7 purchase totals =	$647.42		$694.5609	$694.56	$694.60	$694.60