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	$137.64	6.131%	$146.0787	$146.08	$146.10	$146.10
Purchase #2	$191.85	8.594%	$208.3376	$208.34	$208.35	$208.30
Purchase #3	$205.81	4.642%	$215.3637	$215.36	$215.35	$215.40
Purchase #4	$59.79	12.238%	$67.1071	$67.11	$67.10	$67.10
Purchase #5	$89.46	5.189%	$94.1021	$94.10	$94.10	$94.10
Purchase #6	$79.43	11.687%	$88.713	$88.71	$88.70	$88.70
Purchase #7	$53.68	10.471%	$59.3008	$59.30	$59.30	$59.30
7 purchase totals =	$817.66		$879.0030	$879.00	$879.00	$879.00