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	$215.76	12.864%	$243.5154	$243.52	$243.50	$243.50
Purchase #2	$7.26	8.120%	$7.8495	$7.85	$7.85	$7.80
Purchase #3	$25.86	13.205%	$29.2748	$29.27	$29.25	$29.30
Purchase #4	$123.76	4.642%	$129.5049	$129.50	$129.50	$129.50
Purchase #5	$104.61	7.571%	$112.53	$112.53	$112.55	$112.50
Purchase #6	$62.79	6.870%	$67.1037	$67.10	$67.10	$67.10
Purchase #7	$192.91	12.279%	$216.5974	$216.60	$216.60	$216.60
7 purchase totals =	$732.95		$806.3757	$806.37	$806.35	$806.30