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	$55.83	8.289%	$60.4577	$60.46	$60.45	$60.50
Purchase #2	$173.27	4.705%	$181.4224	$181.42	$181.40	$181.40
Purchase #3	$246.67	11.695%	$275.5181	$275.52	$275.50	$275.50
Purchase #4	$221.40	11.391%	$246.6197	$246.62	$246.60	$246.60
Purchase #5	$40.97	4.199%	$42.6903	$42.69	$42.70	$42.70
Purchase #6	$137.75	10.406%	$152.0843	$152.08	$152.10	$152.10
Purchase #7	$202.46	5.145%	$212.8766	$212.88	$212.90	$212.90
7 purchase totals =	$1,078.35		$1,171.6691	$1,171.67	$1,171.65	$1,171.70