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	$142.43	11.704%	$159.1	$159.10	$159.10	$159.10
Purchase #2	$249.33	5.571%	$263.2202	$263.22	$263.20	$263.20
Purchase #3	$237.93	3.356%	$245.9149	$245.91	$245.90	$245.90
Purchase #4	$188.29	11.356%	$209.6722	$209.67	$209.65	$209.70
Purchase #5	$74.90	9.563%	$82.0627	$82.06	$82.05	$82.10
Purchase #6	$73.76	6.380%	$78.4659	$78.47	$78.45	$78.50
Purchase #7	$21.64	11.499%	$24.1284	$24.13	$24.15	$24.10
7 purchase totals =	$988.28		$1,062.5643	$1,062.56	$1,062.50	$1,062.60