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	$105.50	11.213%	$117.3297	$117.33	$117.35	$117.30
Purchase #2	$55.68	6.553%	$59.3287	$59.33	$59.35	$59.30
Purchase #3	$203.83	7.270%	$218.6484	$218.65	$218.65	$218.60
Purchase #4	$175.61	5.529%	$185.3195	$185.32	$185.30	$185.30
Purchase #5	$145.64	3.135%	$150.2058	$150.21	$150.20	$150.20
Purchase #6	$66.76	8.449%	$72.4006	$72.40	$72.40	$72.40
Purchase #7	$200.85	11.666%	$224.2812	$224.28	$224.30	$224.30
7 purchase totals =	$953.87		$1,027.5139	$1,027.52	$1,027.55	$1,027.40