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	$162.84	9.566%	$178.4173	$178.42	$178.40	$178.40
Purchase #2	$175.85	5.705%	$185.8822	$185.88	$185.90	$185.90
Purchase #3	$27.74	12.632%	$31.2441	$31.24	$31.25	$31.20
Purchase #4	$41.40	3.767%	$42.9595	$42.96	$42.95	$43.00
Purchase #5	$25.34	12.585%	$28.529	$28.53	$28.55	$28.50
Purchase #6	$159.47	12.838%	$179.9428	$179.94	$179.95	$179.90
Purchase #7	$52.37	3.611%	$54.2611	$54.26	$54.25	$54.30
7 purchase totals =	$645.01		$701.2360	$701.23	$701.25	$701.20