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	$241.54	6.217%	$256.5565	$256.56	$256.55	$256.60
Purchase #2	$48.41	11.337%	$53.8982	$53.90	$53.90	$53.90
Purchase #3	$212.91	6.684%	$227.1409	$227.14	$227.15	$227.10
Purchase #4	$98.73	10.608%	$109.2033	$109.20	$109.20	$109.20
Purchase #5	$54.46	4.696%	$57.0174	$57.02	$57.00	$57.00
Purchase #6	$104.92	4.760%	$109.9142	$109.91	$109.90	$109.90
Purchase #7	$166.64	12.594%	$187.6266	$187.63	$187.65	$187.60
7 purchase totals =	$927.61		$1,001.3571	$1,001.36	$1,001.35	$1,001.30