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	$197.43	12.654%	$222.4128	$222.41	$222.40	$222.40
Purchase #2	$57.27	9.431%	$62.6711	$62.67	$62.65	$62.70
Purchase #3	$200.65	11.334%	$223.3917	$223.39	$223.40	$223.40
Purchase #4	$167.61	13.278%	$189.8653	$189.87	$189.85	$189.90
Purchase #5	$163.75	12.163%	$183.6669	$183.67	$183.65	$183.70
Purchase #6	$45.71	3.755%	$47.4264	$47.43	$47.45	$47.40
Purchase #7	$126.36	10.276%	$139.3448	$139.34	$139.35	$139.30
7 purchase totals =	$958.78		$1,068.7790	$1,068.78	$1,068.75	$1,068.80