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	$47.72	10.483%	$52.7225	$52.72	$52.70	$52.70
Purchase #2	$91.83	8.193%	$99.3536	$99.35	$99.35	$99.40
Purchase #3	$101.55	7.393%	$109.0576	$109.06	$109.05	$109.10
Purchase #4	$60.71	4.823%	$63.638	$63.64	$63.65	$63.60
Purchase #5	$36.38	9.269%	$39.7521	$39.75	$39.75	$39.80
Purchase #6	$134.82	9.112%	$147.1048	$147.10	$147.10	$147.10
Purchase #7	$173.82	5.147%	$182.7665	$182.77	$182.75	$182.80
7 purchase totals =	$646.83		$694.3951	$694.39	$694.35	$694.50