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	$41.69	3.803%	$43.2755	$43.28	$43.30	$43.30
Purchase #2	$250.37	12.162%	$280.82	$280.82	$280.80	$280.80
Purchase #3	$50.72	6.752%	$54.1446	$54.14	$54.15	$54.10
Purchase #4	$67.59	3.168%	$69.7313	$69.73	$69.75	$69.70
Purchase #5	$87.81	6.372%	$93.4053	$93.41	$93.40	$93.40
Purchase #6	$167.93	6.374%	$178.6339	$178.63	$178.65	$178.60
Purchase #7	$147.67	10.307%	$162.8903	$162.89	$162.90	$162.90
7 purchase totals =	$813.78		$882.9009	$882.90	$882.95	$882.80