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	$142.93	13.555%	$162.3042	$162.30	$162.30	$162.30
Purchase #2	$161.97	3.360%	$167.4122	$167.41	$167.40	$167.40
Purchase #3	$29.92	10.505%	$33.0631	$33.06	$33.05	$33.10
Purchase #4	$10.43	7.261%	$11.1873	$11.19	$11.20	$11.20
Purchase #5	$96.61	9.474%	$105.7628	$105.76	$105.75	$105.80
Purchase #6	$180.37	8.827%	$196.2913	$196.29	$196.30	$196.30
Purchase #7	$234.58	7.352%	$251.8263	$251.83	$251.85	$251.80
7 purchase totals =	$856.81		$927.8472	$927.84	$927.85	$927.90