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	$100.99	4.240%	$105.272	$105.27	$105.25	$105.30
Purchase #2	$107.38	6.455%	$114.3114	$114.31	$114.30	$114.30
Purchase #3	$44.59	10.163%	$49.1217	$49.12	$49.10	$49.10
Purchase #4	$172.55	7.288%	$185.1254	$185.13	$185.15	$185.10
Purchase #5	$185.39	12.134%	$207.8852	$207.89	$207.90	$207.90
Purchase #6	$240.33	8.129%	$259.8664	$259.87	$259.85	$259.90
Purchase #7	$243.86	5.314%	$256.8187	$256.82	$256.80	$256.80
7 purchase totals =	$1,095.09		$1,178.4008	$1,178.41	$1,178.35	$1,178.40