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	$104.91	5.410%	$110.5856	$110.59	$110.60	$110.60
Purchase #2	$79.99	3.536%	$82.8184	$82.82	$82.80	$82.80
Purchase #3	$49.46	3.339%	$51.1115	$51.11	$51.10	$51.10
Purchase #4	$71.36	10.416%	$78.7929	$78.79	$78.80	$78.80
Purchase #5	$102.60	6.518%	$109.2875	$109.29	$109.30	$109.30
Purchase #6	$147.40	10.199%	$162.4333	$162.43	$162.45	$162.40
Purchase #7	$132.35	5.500%	$139.6293	$139.63	$139.65	$139.60
7 purchase totals =	$688.07		$734.6585	$734.66	$734.70	$734.60