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	$122.27	3.766%	$126.8747	$126.87	$126.85	$126.90
Purchase #2	$149.70	11.647%	$167.1356	$167.14	$167.15	$167.10
Purchase #3	$238.49	7.439%	$256.2313	$256.23	$256.25	$256.20
Purchase #4	$95.39	4.669%	$99.8438	$99.84	$99.85	$99.80
Purchase #5	$122.52	5.154%	$128.8347	$128.83	$128.85	$128.80
Purchase #6	$8.72	4.273%	$9.0926	$9.09	$9.10	$9.10
Purchase #7	$100.73	4.474%	$105.2367	$105.24	$105.25	$105.20
7 purchase totals =	$837.82		$893.2494	$893.24	$893.30	$893.10