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	$89.54	11.210%	$99.5774	$99.58	$99.60	$99.60
Purchase #2	$145.69	11.354%	$162.2316	$162.23	$162.25	$162.20
Purchase #3	$242.36	10.720%	$268.341	$268.34	$268.35	$268.30
Purchase #4	$113.99	9.228%	$124.509	$124.51	$124.50	$124.50
Purchase #5	$59.65	8.333%	$64.6206	$64.62	$64.60	$64.60
Purchase #6	$94.35	5.297%	$99.3477	$99.35	$99.35	$99.30
Purchase #7	$173.73	10.184%	$191.4227	$191.42	$191.40	$191.40
7 purchase totals =	$919.31		$1,010.0500	$1,010.05	$1,010.05	$1,009.90