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	$78.51	8.490%	$85.1755	$85.18	$85.20	$85.20
Purchase #2	$151.79	12.724%	$171.1038	$171.10	$171.10	$171.10
Purchase #3	$229.49	11.336%	$255.505	$255.51	$255.50	$255.50
Purchase #4	$65.72	5.512%	$69.3425	$69.34	$69.35	$69.30
Purchase #5	$124.88	9.169%	$136.3302	$136.33	$136.35	$136.30
Purchase #6	$249.27	13.288%	$282.393	$282.39	$282.40	$282.40
Purchase #7	$112.27	6.418%	$119.4755	$119.48	$119.50	$119.50
7 purchase totals =	$1,011.93		$1,119.3255	$1,119.33	$1,119.40	$1,119.30