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	$53.40	11.478%	$59.5293	$59.53	$59.55	$59.50
Purchase #2	$98.60	8.284%	$106.768	$106.77	$106.75	$106.80
Purchase #3	$25.65	8.189%	$27.7505	$27.75	$27.75	$27.80
Purchase #4	$28.91	13.686%	$32.8666	$32.87	$32.85	$32.90
Purchase #5	$200.60	7.247%	$215.1375	$215.14	$215.15	$215.10
Purchase #6	$71.54	12.330%	$80.3609	$80.36	$80.35	$80.40
Purchase #7	$187.91	12.386%	$211.1845	$211.18	$211.20	$211.20
7 purchase totals =	$666.61		$733.5973	$733.60	$733.60	$733.70