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	$225.36	5.685%	$238.1717	$238.17	$238.15	$238.20
Purchase #2	$206.46	13.288%	$233.8944	$233.89	$233.90	$233.90
Purchase #3	$55.71	8.179%	$60.2665	$60.27	$60.25	$60.30
Purchase #4	$139.88	6.746%	$149.3163	$149.32	$149.30	$149.30
Purchase #5	$191.32	12.461%	$215.1604	$215.16	$215.15	$215.20
Purchase #6	$124.88	6.140%	$132.5476	$132.55	$132.55	$132.50
Purchase #7	$149.80	13.182%	$169.5466	$169.55	$169.55	$169.50
7 purchase totals =	$1,093.41		$1,198.9035	$1,198.91	$1,198.85	$1,198.90