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	$155.88	4.711%	$163.2235	$163.22	$163.20	$163.20
Purchase #2	$51.83	4.573%	$54.2002	$54.20	$54.20	$54.20
Purchase #3	$51.27	6.693%	$54.7015	$54.70	$54.70	$54.70
Purchase #4	$89.66	7.584%	$96.4598	$96.46	$96.45	$96.50
Purchase #5	$167.37	12.673%	$188.5808	$188.58	$188.60	$188.60
Purchase #6	$126.70	3.573%	$131.227	$131.23	$131.25	$131.20
Purchase #7	$31.27	9.435%	$34.2203	$34.22	$34.20	$34.20
7 purchase totals =	$673.98		$722.6131	$722.61	$722.60	$722.60