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	$165.61	9.760%	$181.7735	$181.77	$181.75	$181.80
Purchase #2	$232.60	9.681%	$255.118	$255.12	$255.10	$255.10
Purchase #3	$33.87	9.243%	$37.0006	$37.00	$37.00	$37.00
Purchase #4	$101.64	10.710%	$112.5256	$112.53	$112.55	$112.50
Purchase #5	$124.29	8.669%	$135.0647	$135.06	$135.05	$135.10
Purchase #6	$67.90	7.354%	$72.8934	$72.89	$72.90	$72.90
Purchase #7	$206.96	4.322%	$215.9048	$215.90	$215.90	$215.90
7 purchase totals =	$932.87		$1,010.2806	$1,010.27	$1,010.25	$1,010.30