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	$112.74	13.318%	$127.7547	$127.75	$127.75	$127.80
Purchase #2	$19.48	3.261%	$20.1152	$20.12	$20.10	$20.10
Purchase #3	$116.39	6.862%	$124.3767	$124.38	$124.40	$124.40
Purchase #4	$129.93	12.561%	$146.2505	$146.25	$146.25	$146.30
Purchase #5	$249.31	12.462%	$280.379	$280.38	$280.40	$280.40
Purchase #6	$107.64	11.373%	$119.8819	$119.88	$119.90	$119.90
Purchase #7	$84.29	4.723%	$88.271	$88.27	$88.25	$88.30
7 purchase totals =	$819.78		$907.0290	$907.03	$907.05	$907.20