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	$179.86	9.159%	$196.3334	$196.33	$196.35	$196.30
Purchase #2	$242.25	7.234%	$259.7744	$259.77	$259.75	$259.80
Purchase #3	$216.64	13.812%	$246.5623	$246.56	$246.55	$246.60
Purchase #4	$54.80	9.303%	$59.898	$59.90	$59.90	$59.90
Purchase #5	$87.35	8.791%	$95.0289	$95.03	$95.05	$95.00
Purchase #6	$250.74	4.224%	$261.3313	$261.33	$261.35	$261.30
Purchase #7	$168.69	6.730%	$180.0428	$180.04	$180.05	$180.00
7 purchase totals =	$1,200.33		$1,298.9711	$1,298.96	$1,299.00	$1,298.90