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	$232.60	5.242%	$244.7929	$244.79	$244.80	$244.80
Purchase #2	$172.85	6.242%	$183.6393	$183.64	$183.65	$183.60
Purchase #3	$66.30	6.104%	$70.347	$70.35	$70.35	$70.30
Purchase #4	$187.34	4.801%	$196.3342	$196.33	$196.35	$196.30
Purchase #5	$240.83	3.671%	$249.6709	$249.67	$249.65	$249.70
Purchase #6	$72.84	8.525%	$79.0496	$79.05	$79.05	$79.00
Purchase #7	$59.39	10.396%	$65.5642	$65.56	$65.55	$65.60
7 purchase totals =	$1,032.15		$1,089.3981	$1,089.39	$1,089.40	$1,089.30