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	$166.78	4.379%	$174.0833	$174.08	$174.10	$174.10
Purchase #2	$214.43	12.306%	$240.8178	$240.82	$240.80	$240.80
Purchase #3	$57.27	11.839%	$64.0502	$64.05	$64.05	$64.10
Purchase #4	$36.42	11.833%	$40.7296	$40.73	$40.75	$40.70
Purchase #5	$200.48	7.601%	$215.7185	$215.72	$215.70	$215.70
Purchase #6	$48.35	6.118%	$51.3081	$51.31	$51.30	$51.30
Purchase #7	$199.93	9.463%	$218.8494	$218.85	$218.85	$218.80
7 purchase totals =	$923.66		$1,005.5569	$1,005.56	$1,005.55	$1,005.50