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	$136.37	3.805%	$141.5589	$141.56	$141.55	$141.60
Purchase #2	$127.58	7.311%	$136.9074	$136.91	$136.90	$136.90
Purchase #3	$58.72	6.657%	$62.629	$62.63	$62.65	$62.60
Purchase #4	$10.50	5.476%	$11.075	$11.08	$11.10	$11.10
Purchase #5	$43.43	11.423%	$48.391	$48.39	$48.40	$48.40
Purchase #6	$211.96	7.786%	$228.4632	$228.46	$228.45	$228.50
Purchase #7	$120.37	6.538%	$128.2398	$128.24	$128.25	$128.20
7 purchase totals =	$708.93		$757.2643	$757.27	$757.30	$757.30