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	$57.54	6.317%	$61.1748	$61.17	$61.15	$61.20
Purchase #2	$230.48	12.520%	$259.3361	$259.34	$259.35	$259.30
Purchase #3	$88.94	12.298%	$99.8778	$99.88	$99.90	$99.90
Purchase #4	$219.95	13.410%	$249.4453	$249.45	$249.45	$249.40
Purchase #5	$124.64	10.425%	$137.6337	$137.63	$137.65	$137.60
Purchase #6	$51.72	10.496%	$57.1485	$57.15	$57.15	$57.10
Purchase #7	$207.76	3.515%	$215.0628	$215.06	$215.05	$215.10
7 purchase totals =	$981.03		$1,079.6790	$1,079.68	$1,079.70	$1,079.60