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	$156.25	6.223%	$165.9734	$165.97	$165.95	$166.00
Purchase #2	$216.88	5.264%	$228.2966	$228.30	$228.30	$228.30
Purchase #3	$150.33	13.756%	$171.0094	$171.01	$171.00	$171.00
Purchase #4	$153.39	6.171%	$162.8557	$162.86	$162.85	$162.90
Purchase #5	$207.63	11.309%	$231.1109	$231.11	$231.10	$231.10
Purchase #6	$83.71	7.105%	$89.6576	$89.66	$89.65	$89.70
Purchase #7	$166.32	5.462%	$175.4044	$175.40	$175.40	$175.40
7 purchase totals =	$1,134.51		$1,224.3080	$1,224.31	$1,224.25	$1,224.40