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	$174.30	7.582%	$187.5154	$187.52	$187.50	$187.50
Purchase #2	$205.40	4.770%	$215.1976	$215.20	$215.20	$215.20
Purchase #3	$185.87	3.790%	$192.9145	$192.91	$192.90	$192.90
Purchase #4	$49.71	10.184%	$54.7725	$54.77	$54.75	$54.80
Purchase #5	$35.26	9.107%	$38.4711	$38.47	$38.45	$38.50
Purchase #6	$27.37	13.760%	$31.1361	$31.14	$31.15	$31.10
Purchase #7	$229.95	11.399%	$256.162	$256.16	$256.15	$256.20
7 purchase totals =	$907.86		$976.1692	$976.17	$976.10	$976.20