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	$44.79	8.346%	$48.5282	$48.53	$48.55	$48.50
Purchase #2	$32.74	10.445%	$36.1597	$36.16	$36.15	$36.20
Purchase #3	$43.52	11.235%	$48.4095	$48.41	$48.40	$48.40
Purchase #4	$85.90	12.780%	$96.878	$96.88	$96.90	$96.90
Purchase #5	$168.64	13.757%	$191.8398	$191.84	$191.85	$191.80
Purchase #6	$53.32	6.723%	$56.9047	$56.90	$56.90	$56.90
Purchase #7	$48.31	11.618%	$53.9227	$53.92	$53.90	$53.90
7 purchase totals =	$477.22		$532.6426	$532.64	$532.65	$532.60