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	$174.40	12.497%	$196.1948	$196.19	$196.20	$196.20
Purchase #2	$135.82	3.558%	$140.6525	$140.65	$140.65	$140.70
Purchase #3	$52.68	12.298%	$59.1586	$59.16	$59.15	$59.20
Purchase #4	$21.57	12.279%	$24.2186	$24.22	$24.20	$24.20
Purchase #5	$84.33	10.127%	$92.8701	$92.87	$92.85	$92.90
Purchase #6	$95.87	11.460%	$106.8567	$106.86	$106.85	$106.90
Purchase #7	$166.31	8.695%	$180.7707	$180.77	$180.75	$180.80
7 purchase totals =	$730.98		$800.7220	$800.72	$800.65	$800.90