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	$50.61	8.169%	$54.7443	$54.74	$54.75	$54.70
Purchase #2	$152.95	8.153%	$165.42	$165.42	$165.40	$165.40
Purchase #3	$114.88	7.562%	$123.5672	$123.57	$123.55	$123.60
Purchase #4	$16.25	11.499%	$18.1186	$18.12	$18.10	$18.10
Purchase #5	$181.54	4.704%	$190.0796	$190.08	$190.10	$190.10
Purchase #6	$119.42	4.279%	$124.53	$124.53	$124.55	$124.50
Purchase #7	$213.79	5.627%	$225.82	$225.82	$225.80	$225.80
7 purchase totals =	$849.44		$902.2797	$902.28	$902.25	$902.20