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	$179.77	13.705%	$204.4075	$204.41	$204.40	$204.40
Purchase #2	$38.28	9.426%	$41.8883	$41.89	$41.90	$41.90
Purchase #3	$89.50	5.738%	$94.6355	$94.64	$94.65	$94.60
Purchase #4	$42.45	12.230%	$47.6416	$47.64	$47.65	$47.60
Purchase #5	$161.84	12.655%	$182.3209	$182.32	$182.30	$182.30
Purchase #6	$217.82	8.275%	$235.8446	$235.84	$235.85	$235.80
Purchase #7	$211.30	5.780%	$223.5131	$223.51	$223.50	$223.50
7 purchase totals =	$940.96		$1,030.2515	$1,030.25	$1,030.25	$1,030.10