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	$115.30	5.865%	$122.0623	$122.06	$122.05	$122.10
Purchase #2	$6.74	4.103%	$7.0165	$7.02	$7.00	$7.00
Purchase #3	$126.53	7.597%	$136.1425	$136.14	$136.15	$136.10
Purchase #4	$188.94	3.790%	$196.1008	$196.10	$196.10	$196.10
Purchase #5	$186.48	5.589%	$196.9024	$196.90	$196.90	$196.90
Purchase #6	$231.98	7.696%	$249.8332	$249.83	$249.85	$249.80
Purchase #7	$93.60	12.827%	$105.6061	$105.61	$105.60	$105.60
7 purchase totals =	$949.57		$1,013.6638	$1,013.66	$1,013.65	$1,013.60