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	$50.45	8.107%	$54.54	$54.54	$54.55	$54.50
Purchase #2	$28.38	3.743%	$29.4423	$29.44	$29.45	$29.40
Purchase #3	$85.86	5.362%	$90.4638	$90.46	$90.45	$90.50
Purchase #4	$218.40	4.380%	$227.9659	$227.97	$227.95	$228.00
Purchase #5	$83.73	5.768%	$88.5595	$88.56	$88.55	$88.60
Purchase #6	$48.81	9.868%	$53.6266	$53.63	$53.65	$53.60
Purchase #7	$103.64	5.774%	$109.6242	$109.62	$109.60	$109.60
7 purchase totals =	$619.27		$654.2223	$654.22	$654.20	$654.20