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	$168.56	3.550%	$174.5439	$174.54	$174.55	$174.50
Purchase #2	$162.73	7.572%	$175.0519	$175.05	$175.05	$175.10
Purchase #3	$171.42	3.536%	$177.4814	$177.48	$177.50	$177.50
Purchase #4	$180.55	12.516%	$203.1476	$203.15	$203.15	$203.10
Purchase #5	$124.92	11.797%	$139.6568	$139.66	$139.65	$139.70
Purchase #6	$51.83	5.526%	$54.6941	$54.69	$54.70	$54.70
Purchase #7	$51.72	3.357%	$53.4562	$53.46	$53.45	$53.50
7 purchase totals =	$911.73		$978.0319	$978.03	$978.05	$978.10