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	$250.39	13.545%	$284.3053	$284.31	$284.30	$284.30
Purchase #2	$123.39	12.524%	$138.8434	$138.84	$138.85	$138.80
Purchase #3	$70.95	4.781%	$74.3421	$74.34	$74.35	$74.30
Purchase #4	$86.89	3.425%	$89.866	$89.87	$89.85	$89.90
Purchase #5	$211.76	5.693%	$223.8155	$223.82	$223.80	$223.80
Purchase #6	$89.61	12.806%	$101.0855	$101.09	$101.10	$101.10
Purchase #7	$212.48	12.867%	$239.8198	$239.82	$239.80	$239.80
7 purchase totals =	$1,045.47		$1,152.0776	$1,152.09	$1,152.05	$1,152.00