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	$245.84	7.135%	$263.3807	$263.38	$263.40	$263.40
Purchase #2	$78.82	12.650%	$88.7907	$88.79	$88.80	$88.80
Purchase #3	$85.46	10.622%	$94.5376	$94.54	$94.55	$94.50
Purchase #4	$27.26	4.720%	$28.5467	$28.55	$28.55	$28.50
Purchase #5	$91.31	9.601%	$100.0767	$100.08	$100.10	$100.10
Purchase #6	$38.75	5.795%	$40.9956	$41.00	$41.00	$41.00
Purchase #7	$127.27	11.853%	$142.3553	$142.36	$142.35	$142.40
7 purchase totals =	$694.71		$758.6833	$758.70	$758.75	$758.70