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	$148.69	3.552%	$153.9715	$153.97	$153.95	$154.00
Purchase #2	$38.31	11.276%	$42.6298	$42.63	$42.65	$42.60
Purchase #3	$83.36	7.868%	$89.9188	$89.92	$89.90	$89.90
Purchase #4	$79.93	12.392%	$89.8349	$89.83	$89.85	$89.80
Purchase #5	$74.80	10.344%	$82.5373	$82.54	$82.55	$82.50
Purchase #6	$30.31	10.435%	$33.4728	$33.47	$33.45	$33.50
Purchase #7	$162.56	12.705%	$183.2132	$183.21	$183.20	$183.20
7 purchase totals =	$617.96		$675.5783	$675.57	$675.55	$675.50