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	$224.40	10.740%	$248.5006	$248.50	$248.50	$248.50
Purchase #2	$45.42	6.429%	$48.3401	$48.34	$48.35	$48.30
Purchase #3	$53.98	4.458%	$56.3864	$56.39	$56.40	$56.40
Purchase #4	$149.52	4.493%	$156.2379	$156.24	$156.25	$156.20
Purchase #5	$176.93	4.281%	$184.5044	$184.50	$184.50	$184.50
Purchase #6	$43.28	7.123%	$46.3628	$46.36	$46.35	$46.40
Purchase #7	$175.76	11.757%	$196.4241	$196.42	$196.40	$196.40
7 purchase totals =	$869.29		$936.7563	$936.75	$936.75	$936.70