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	$98.90	4.845%	$103.6917	$103.69	$103.70	$103.70
Purchase #2	$201.64	9.457%	$220.7091	$220.71	$220.70	$220.70
Purchase #3	$48.25	8.428%	$52.3165	$52.32	$52.30	$52.30
Purchase #4	$32.82	13.182%	$37.1463	$37.15	$37.15	$37.10
Purchase #5	$17.64	7.428%	$18.9503	$18.95	$18.95	$19.00
Purchase #6	$106.79	4.586%	$111.6874	$111.69	$111.70	$111.70
Purchase #7	$181.65	3.124%	$187.3247	$187.32	$187.30	$187.30
7 purchase totals =	$687.69		$731.8260	$731.83	$731.80	$731.80