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	$90.61	8.261%	$98.0953	$98.10	$98.10	$98.10
Purchase #2	$24.68	13.720%	$28.0661	$28.07	$28.05	$28.10
Purchase #3	$67.46	7.362%	$72.4264	$72.43	$72.45	$72.40
Purchase #4	$238.88	4.273%	$249.0873	$249.09	$249.10	$249.10
Purchase #5	$191.50	7.524%	$205.9085	$205.91	$205.90	$205.90
Purchase #6	$18.75	13.333%	$21.2499	$21.25	$21.25	$21.20
Purchase #7	$52.86	6.613%	$56.3556	$56.36	$56.35	$56.40
7 purchase totals =	$684.74		$731.1891	$731.21	$731.20	$731.20