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	$42.68	6.544%	$45.473	$45.47	$45.45	$45.50
Purchase #2	$82.37	7.396%	$88.4621	$88.46	$88.45	$88.50
Purchase #3	$182.42	6.654%	$194.5582	$194.56	$194.55	$194.60
Purchase #4	$125.64	6.225%	$133.4611	$133.46	$133.45	$133.50
Purchase #5	$246.80	13.361%	$279.7749	$279.77	$279.75	$279.80
Purchase #6	$96.94	9.681%	$106.3248	$106.32	$106.30	$106.30
Purchase #7	$142.63	9.695%	$156.458	$156.46	$156.45	$156.50
7 purchase totals =	$919.48		$1,004.5121	$1,004.50	$1,004.40	$1,004.70