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	$103.29	8.667%	$112.2421	$112.24	$112.25	$112.20
Purchase #2	$92.41	6.669%	$98.5728	$98.57	$98.55	$98.60
Purchase #3	$121.57	9.582%	$133.2188	$133.22	$133.20	$133.20
Purchase #4	$130.68	8.744%	$142.1067	$142.11	$142.10	$142.10
Purchase #5	$136.81	6.651%	$145.9092	$145.91	$145.90	$145.90
Purchase #6	$147.83	8.415%	$160.2699	$160.27	$160.25	$160.30
Purchase #7	$52.72	13.633%	$59.9073	$59.91	$59.90	$59.90
7 purchase totals =	$785.31		$852.2268	$852.23	$852.15	$852.20