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	$30.64	5.521%	$32.3316	$32.33	$32.35	$32.30
Purchase #2	$222.86	4.612%	$233.1383	$233.14	$233.15	$233.10
Purchase #3	$95.97	4.274%	$100.0718	$100.07	$100.05	$100.10
Purchase #4	$159.83	7.135%	$171.2339	$171.23	$171.25	$171.20
Purchase #5	$68.32	6.289%	$72.6166	$72.62	$72.60	$72.60
Purchase #6	$197.63	4.620%	$206.7605	$206.76	$206.75	$206.80
Purchase #7	$5.79	10.288%	$6.3857	$6.39	$6.40	$6.40
7 purchase totals =	$781.04		$822.5384	$822.54	$822.55	$822.50