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	$220.75	5.351%	$232.5623	$232.56	$232.55	$232.60
Purchase #2	$39.91	6.729%	$42.5955	$42.60	$42.60	$42.60
Purchase #3	$131.83	13.808%	$150.0331	$150.03	$150.05	$150.00
Purchase #4	$141.69	10.756%	$156.9302	$156.93	$156.95	$156.90
Purchase #5	$77.80	5.669%	$82.2105	$82.21	$82.20	$82.20
Purchase #6	$161.90	3.720%	$167.9227	$167.92	$167.90	$167.90
Purchase #7	$249.82	5.537%	$263.6525	$263.65	$263.65	$263.70
7 purchase totals =	$1,023.70		$1,095.9068	$1,095.90	$1,095.90	$1,095.90