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	$175.89	6.352%	$187.0625	$187.06	$187.05	$187.10
Purchase #2	$39.80	4.728%	$41.6817	$41.68	$41.70	$41.70
Purchase #3	$65.47	12.864%	$73.8921	$73.89	$73.90	$73.90
Purchase #4	$230.96	6.255%	$245.4065	$245.41	$245.40	$245.40
Purchase #5	$203.25	10.808%	$225.2173	$225.22	$225.20	$225.20
Purchase #6	$203.55	9.383%	$222.6491	$222.65	$222.65	$222.60
Purchase #7	$152.83	10.114%	$168.2872	$168.29	$168.30	$168.30
7 purchase totals =	$1,071.75		$1,164.1964	$1,164.20	$1,164.20	$1,164.20