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	$84.73	8.128%	$91.6169	$91.62	$91.60	$91.60
Purchase #2	$171.95	4.451%	$179.6035	$179.60	$179.60	$179.60
Purchase #3	$168.96	11.481%	$188.3583	$188.36	$188.35	$188.40
Purchase #4	$70.84	11.588%	$79.0489	$79.05	$79.05	$79.00
Purchase #5	$105.54	13.295%	$119.5715	$119.57	$119.55	$119.60
Purchase #6	$27.59	6.539%	$29.3941	$29.39	$29.40	$29.40
Purchase #7	$52.86	12.201%	$59.3094	$59.31	$59.30	$59.30
7 purchase totals =	$682.47		$746.9026	$746.90	$746.85	$746.90