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	$22.41	11.399%	$24.9645	$24.96	$24.95	$25.00
Purchase #2	$25.90	10.379%	$28.5882	$28.59	$28.60	$28.60
Purchase #3	$207.65	3.710%	$215.3538	$215.35	$215.35	$215.40
Purchase #4	$162.76	11.217%	$181.0168	$181.02	$181.00	$181.00
Purchase #5	$211.69	10.288%	$233.4687	$233.47	$233.45	$233.50
Purchase #6	$91.90	6.478%	$97.8533	$97.85	$97.85	$97.90
Purchase #7	$220.56	3.317%	$227.876	$227.88	$227.90	$227.90
7 purchase totals =	$942.87		$1,009.1213	$1,009.12	$1,009.10	$1,009.30