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	$153.84	11.369%	$171.3301	$171.33	$171.35	$171.30
Purchase #2	$230.25	3.701%	$238.7716	$238.77	$238.75	$238.80
Purchase #3	$73.33	12.696%	$82.64	$82.64	$82.65	$82.60
Purchase #4	$119.93	7.133%	$128.4846	$128.48	$128.50	$128.50
Purchase #5	$181.55	4.394%	$189.5273	$189.53	$189.55	$189.50
Purchase #6	$156.44	10.158%	$172.3312	$172.33	$172.35	$172.30
Purchase #7	$55.59	13.595%	$63.1475	$63.15	$63.15	$63.10
7 purchase totals =	$970.93		$1,046.2323	$1,046.23	$1,046.30	$1,046.10