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	$185.92	5.796%	$196.6959	$196.70	$196.70	$196.70
Purchase #2	$65.42	10.650%	$72.3872	$72.39	$72.40	$72.40
Purchase #3	$62.52	10.338%	$68.9833	$68.98	$69.00	$69.00
Purchase #4	$30.64	12.347%	$34.4231	$34.42	$34.40	$34.40
Purchase #5	$237.49	11.278%	$264.2741	$264.27	$264.25	$264.30
Purchase #6	$75.57	13.263%	$85.5928	$85.59	$85.60	$85.60
Purchase #7	$246.39	10.390%	$271.9899	$271.99	$272.00	$272.00
7 purchase totals =	$903.95		$994.3463	$994.34	$994.35	$994.40