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	$12.42	5.181%	$13.0635	$13.06	$13.05	$13.10
Purchase #2	$55.34	12.242%	$62.1147	$62.11	$62.10	$62.10
Purchase #3	$98.29	6.176%	$104.3604	$104.36	$104.35	$104.40
Purchase #4	$208.94	9.270%	$228.3087	$228.31	$228.30	$228.30
Purchase #5	$144.89	4.167%	$150.9276	$150.93	$150.95	$150.90
Purchase #6	$25.66	10.170%	$28.2696	$28.27	$28.25	$28.30
Purchase #7	$148.39	11.824%	$165.9356	$165.94	$165.95	$165.90
7 purchase totals =	$693.93		$752.9801	$752.98	$752.95	$753.00