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	$208.32	11.244%	$231.7435	$231.74	$231.75	$231.70
Purchase #2	$212.78	8.526%	$230.9216	$230.92	$230.90	$230.90
Purchase #3	$57.38	7.734%	$61.8178	$61.82	$61.80	$61.80
Purchase #4	$43.59	8.812%	$47.4312	$47.43	$47.45	$47.40
Purchase #5	$238.56	3.608%	$247.1672	$247.17	$247.15	$247.20
Purchase #6	$84.59	5.347%	$89.113	$89.11	$89.10	$89.10
Purchase #7	$245.92	11.431%	$274.0311	$274.03	$274.05	$274.00
7 purchase totals =	$1,091.14		$1,182.2254	$1,182.22	$1,182.20	$1,182.10