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	$83.68	5.284%	$88.1017	$88.10	$88.10	$88.10
Purchase #2	$71.47	7.572%	$76.8817	$76.88	$76.90	$76.90
Purchase #3	$46.30	13.252%	$52.4357	$52.44	$52.45	$52.40
Purchase #4	$54.46	13.592%	$61.8622	$61.86	$61.85	$61.90
Purchase #5	$70.85	7.380%	$76.0787	$76.08	$76.10	$76.10
Purchase #6	$85.35	4.552%	$89.2351	$89.24	$89.25	$89.20
Purchase #7	$244.36	11.437%	$272.3075	$272.31	$272.30	$272.30
7 purchase totals =	$656.47		$716.9026	$716.91	$716.95	$716.90