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	$13.69	9.838%	$15.0368	$15.04	$15.05	$15.00
Purchase #2	$123.66	11.620%	$138.0293	$138.03	$138.05	$138.00
Purchase #3	$195.28	10.507%	$215.7981	$215.80	$215.80	$215.80
Purchase #4	$145.41	3.727%	$150.8294	$150.83	$150.85	$150.80
Purchase #5	$211.93	11.106%	$235.4669	$235.47	$235.45	$235.50
Purchase #6	$184.68	6.196%	$196.1228	$196.12	$196.10	$196.10
Purchase #7	$218.92	12.144%	$245.5056	$245.51	$245.50	$245.50
7 purchase totals =	$1,093.57		$1,196.7889	$1,196.80	$1,196.80	$1,196.70