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	$206.77	7.104%	$221.4589	$221.46	$221.45	$221.50
Purchase #2	$218.33	13.159%	$247.06	$247.06	$247.05	$247.10
Purchase #3	$31.52	9.261%	$34.4391	$34.44	$34.45	$34.40
Purchase #4	$123.72	3.112%	$127.5702	$127.57	$127.55	$127.60
Purchase #5	$153.75	8.724%	$167.1632	$167.16	$167.15	$167.20
Purchase #6	$82.65	4.234%	$86.1494	$86.15	$86.15	$86.10
Purchase #7	$239.84	7.696%	$258.2981	$258.30	$258.30	$258.30
7 purchase totals =	$1,056.58		$1,142.1389	$1,142.14	$1,142.10	$1,142.20