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	$167.94	4.766%	$175.944	$175.94	$175.95	$175.90
Purchase #2	$186.52	7.419%	$200.3579	$200.36	$200.35	$200.40
Purchase #3	$123.46	3.869%	$128.2367	$128.24	$128.25	$128.20
Purchase #4	$6.97	12.410%	$7.835	$7.84	$7.85	$7.80
Purchase #5	$212.66	5.541%	$224.4435	$224.44	$224.45	$224.40
Purchase #6	$54.27	10.494%	$59.9651	$59.97	$59.95	$60.00
Purchase #7	$90.40	10.169%	$99.5928	$99.59	$99.60	$99.60
7 purchase totals =	$842.22		$896.3750	$896.38	$896.40	$896.30