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	$119.30	6.807%	$127.4208	$127.42	$127.40	$127.40
Purchase #2	$37.82	6.797%	$40.3906	$40.39	$40.40	$40.40
Purchase #3	$107.33	9.535%	$117.5639	$117.56	$117.55	$117.60
Purchase #4	$189.82	9.129%	$207.1487	$207.15	$207.15	$207.10
Purchase #5	$49.45	11.149%	$54.9632	$54.96	$54.95	$55.00
Purchase #6	$213.88	9.701%	$234.6285	$234.63	$234.65	$234.60
Purchase #7	$210.37	6.384%	$223.8	$223.80	$223.80	$223.80
7 purchase totals =	$927.97		$1,005.9157	$1,005.91	$1,005.90	$1,005.90