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	$181.37	12.788%	$204.5636	$204.56	$204.55	$204.60
Purchase #2	$249.30	6.385%	$265.2178	$265.22	$265.20	$265.20
Purchase #3	$88.57	8.598%	$96.1852	$96.19	$96.20	$96.20
Purchase #4	$107.59	13.512%	$122.1276	$122.13	$122.15	$122.10
Purchase #5	$123.90	3.803%	$128.6119	$128.61	$128.60	$128.60
Purchase #6	$170.43	7.399%	$183.0401	$183.04	$183.05	$183.00
Purchase #7	$189.84	3.609%	$196.6913	$196.69	$196.70	$196.70
7 purchase totals =	$1,111.00		$1,196.4375	$1,196.44	$1,196.45	$1,196.40