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	$96.87	13.441%	$109.8903	$109.89	$109.90	$109.90
Purchase #2	$57.84	11.742%	$64.6316	$64.63	$64.65	$64.60
Purchase #3	$104.59	4.339%	$109.1282	$109.13	$109.15	$109.10
Purchase #4	$153.98	5.737%	$162.8138	$162.81	$162.80	$162.80
Purchase #5	$22.91	11.451%	$25.5334	$25.53	$25.55	$25.50
Purchase #6	$155.53	13.450%	$176.4488	$176.45	$176.45	$176.40
Purchase #7	$232.80	11.568%	$259.7303	$259.73	$259.75	$259.70
7 purchase totals =	$824.52		$908.1764	$908.17	$908.25	$908.00