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	$123.56	3.259%	$127.5868	$127.59	$127.60	$127.60
Purchase #2	$66.28	11.404%	$73.8386	$73.84	$73.85	$73.80
Purchase #3	$54.40	7.787%	$58.6361	$58.64	$58.65	$58.60
Purchase #4	$43.95	5.573%	$46.3993	$46.40	$46.40	$46.40
Purchase #5	$105.75	7.599%	$113.7859	$113.79	$113.80	$113.80
Purchase #6	$199.79	9.253%	$218.2766	$218.28	$218.30	$218.30
Purchase #7	$36.99	7.850%	$39.8937	$39.89	$39.90	$39.90
7 purchase totals =	$630.72		$678.4170	$678.43	$678.50	$678.40