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	$98.34	6.707%	$104.9357	$104.94	$104.95	$104.90
Purchase #2	$162.43	9.669%	$178.1354	$178.14	$178.15	$178.10
Purchase #3	$58.78	4.588%	$61.4768	$61.48	$61.50	$61.50
Purchase #4	$127.30	6.798%	$135.9539	$135.95	$135.95	$136.00
Purchase #5	$240.69	4.168%	$250.722	$250.72	$250.70	$250.70
Purchase #6	$215.56	10.854%	$238.9569	$238.96	$238.95	$239.00
Purchase #7	$165.31	12.277%	$185.6051	$185.61	$185.60	$185.60
7 purchase totals =	$1,068.41		$1,155.7858	$1,155.80	$1,155.80	$1,155.80