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	$186.74	12.613%	$210.2935	$210.29	$210.30	$210.30
Purchase #2	$99.54	9.511%	$109.0072	$109.01	$109.00	$109.00
Purchase #3	$174.72	3.153%	$180.2289	$180.23	$180.25	$180.20
Purchase #4	$72.34	8.572%	$78.541	$78.54	$78.55	$78.50
Purchase #5	$187.87	3.705%	$194.8306	$194.83	$194.85	$194.80
Purchase #6	$72.27	6.721%	$77.1273	$77.13	$77.15	$77.10
Purchase #7	$238.49	9.736%	$261.7094	$261.71	$261.70	$261.70
7 purchase totals =	$1,031.97		$1,111.7379	$1,111.74	$1,111.80	$1,111.60