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	$175.93	5.674%	$185.9123	$185.91	$185.90	$185.90
Purchase #2	$168.33	8.493%	$182.6263	$182.63	$182.65	$182.60
Purchase #3	$59.82	6.742%	$63.8531	$63.85	$63.85	$63.90
Purchase #4	$118.64	11.599%	$132.4011	$132.40	$132.40	$132.40
Purchase #5	$91.28	6.134%	$96.8791	$96.88	$96.90	$96.90
Purchase #6	$37.41	6.149%	$39.7103	$39.71	$39.70	$39.70
Purchase #7	$147.86	11.108%	$164.2843	$164.28	$164.30	$164.30
7 purchase totals =	$799.27		$865.6665	$865.66	$865.70	$865.70