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	$62.29	13.765%	$70.8642	$70.86	$70.85	$70.90
Purchase #2	$127.45	7.705%	$137.27	$137.27	$137.25	$137.30
Purchase #3	$162.66	11.479%	$181.3317	$181.33	$181.35	$181.30
Purchase #4	$21.88	5.376%	$23.0563	$23.06	$23.05	$23.10
Purchase #5	$136.61	4.361%	$142.5676	$142.57	$142.55	$142.60
Purchase #6	$32.72	12.474%	$36.8015	$36.80	$36.80	$36.80
Purchase #7	$190.56	11.175%	$211.8551	$211.86	$211.85	$211.90
7 purchase totals =	$734.17		$803.7464	$803.75	$803.70	$803.90