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	$158.66	13.329%	$179.8078	$179.81	$179.80	$179.80
Purchase #2	$171.59	11.363%	$191.0878	$191.09	$191.10	$191.10
Purchase #3	$54.92	11.769%	$61.3835	$61.38	$61.40	$61.40
Purchase #4	$98.78	11.210%	$109.8532	$109.85	$109.85	$109.90
Purchase #5	$226.83	4.859%	$237.8517	$237.85	$237.85	$237.90
Purchase #6	$120.45	5.673%	$127.2831	$127.28	$127.30	$127.30
Purchase #7	$96.28	9.745%	$105.6625	$105.66	$105.65	$105.70
7 purchase totals =	$927.51		$1,012.9296	$1,012.92	$1,012.95	$1,013.10