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	$235.51	9.535%	$257.9659	$257.97	$257.95	$258.00
Purchase #2	$100.81	11.199%	$112.0997	$112.10	$112.10	$112.10
Purchase #3	$150.96	11.495%	$168.3129	$168.31	$168.30	$168.30
Purchase #4	$9.53	6.314%	$10.1317	$10.13	$10.15	$10.10
Purchase #5	$153.82	5.739%	$162.6477	$162.65	$162.65	$162.60
Purchase #6	$162.99	5.435%	$171.8485	$171.85	$171.85	$171.80
Purchase #7	$218.79	13.612%	$248.5717	$248.57	$248.55	$248.60
7 purchase totals =	$1,032.41		$1,131.5781	$1,131.58	$1,131.55	$1,131.50