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	$104.26	7.296%	$111.8668	$111.87	$111.85	$111.90
Purchase #2	$43.77	13.174%	$49.5363	$49.54	$49.55	$49.50
Purchase #3	$84.76	13.125%	$95.8848	$95.88	$95.90	$95.90
Purchase #4	$216.53	4.269%	$225.7737	$225.77	$225.75	$225.80
Purchase #5	$68.99	13.406%	$78.2388	$78.24	$78.25	$78.20
Purchase #6	$238.59	3.216%	$246.2631	$246.26	$246.25	$246.30
Purchase #7	$204.27	3.616%	$211.6564	$211.66	$211.65	$211.70
7 purchase totals =	$961.17		$1,019.2199	$1,019.22	$1,019.20	$1,019.30