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	$68.40	5.111%	$71.8959	$71.90	$71.90	$71.90
Purchase #2	$64.69	12.843%	$72.9981	$73.00	$73.00	$73.00
Purchase #3	$168.86	9.597%	$185.0655	$185.07	$185.05	$185.10
Purchase #4	$100.37	3.702%	$104.0857	$104.09	$104.10	$104.10
Purchase #5	$23.77	6.305%	$25.2687	$25.27	$25.25	$25.30
Purchase #6	$218.66	3.870%	$227.1221	$227.12	$227.10	$227.10
Purchase #7	$82.51	9.245%	$90.138	$90.14	$90.15	$90.10
7 purchase totals =	$727.26		$776.5740	$776.59	$776.55	$776.60