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	$176.38	4.403%	$184.146	$184.15	$184.15	$184.10
Purchase #2	$114.47	7.556%	$123.1194	$123.12	$123.10	$123.10
Purchase #3	$98.31	6.629%	$104.827	$104.83	$104.85	$104.80
Purchase #4	$167.67	8.800%	$182.425	$182.43	$182.45	$182.40
Purchase #5	$73.47	12.853%	$82.9131	$82.91	$82.90	$82.90
Purchase #6	$58.33	4.331%	$60.8563	$60.86	$60.85	$60.90
Purchase #7	$102.32	3.233%	$105.628	$105.63	$105.65	$105.60
7 purchase totals =	$790.95		$843.9148	$843.93	$843.95	$843.80