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	$157.86	7.793%	$170.162	$170.16	$170.15	$170.20
Purchase #2	$151.80	13.134%	$171.7374	$171.74	$171.75	$171.70
Purchase #3	$179.88	9.464%	$196.9038	$196.90	$196.90	$196.90
Purchase #4	$205.98	13.515%	$233.8182	$233.82	$233.80	$233.80
Purchase #5	$211.38	3.440%	$218.6515	$218.65	$218.65	$218.70
Purchase #6	$16.38	11.581%	$18.277	$18.28	$18.30	$18.30
Purchase #7	$172.97	7.818%	$186.4928	$186.49	$186.50	$186.50
7 purchase totals =	$1,096.25		$1,196.0427	$1,196.04	$1,196.05	$1,196.10