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	$219.46	11.166%	$243.9649	$243.96	$243.95	$244.00
Purchase #2	$45.61	9.442%	$49.9165	$49.92	$49.90	$49.90
Purchase #3	$221.57	12.871%	$250.0883	$250.09	$250.10	$250.10
Purchase #4	$101.55	10.207%	$111.9152	$111.92	$111.90	$111.90
Purchase #5	$103.90	10.133%	$114.4282	$114.43	$114.45	$114.40
Purchase #6	$142.57	6.418%	$151.7201	$151.72	$151.70	$151.70
Purchase #7	$216.91	7.367%	$232.8898	$232.89	$232.90	$232.90
7 purchase totals =	$1,051.57		$1,154.9230	$1,154.93	$1,154.90	$1,154.90