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	$64.39	11.139%	$71.5624	$71.56	$71.55	$71.60
Purchase #2	$248.38	4.383%	$259.2665	$259.27	$259.25	$259.30
Purchase #3	$129.95	10.603%	$143.7286	$143.73	$143.75	$143.70
Purchase #4	$221.43	12.282%	$248.626	$248.63	$248.65	$248.60
Purchase #5	$74.97	4.385%	$78.2574	$78.26	$78.25	$78.30
Purchase #6	$240.28	10.591%	$265.7281	$265.73	$265.75	$265.70
Purchase #7	$127.32	12.608%	$143.3725	$143.37	$143.35	$143.40
7 purchase totals =	$1,106.72		$1,210.5415	$1,210.55	$1,210.55	$1,210.60