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	$187.33	5.112%	$196.9063	$196.91	$196.90	$196.90
Purchase #2	$58.65	7.625%	$63.1221	$63.12	$63.10	$63.10
Purchase #3	$21.59	13.386%	$24.48	$24.48	$24.50	$24.50
Purchase #4	$84.68	5.360%	$89.2188	$89.22	$89.20	$89.20
Purchase #5	$219.99	12.763%	$248.0673	$248.07	$248.05	$248.10
Purchase #6	$249.50	6.798%	$266.461	$266.46	$266.45	$266.50
Purchase #7	$109.62	5.107%	$115.2183	$115.22	$115.20	$115.20
7 purchase totals =	$931.36		$1,003.4738	$1,003.48	$1,003.40	$1,003.50