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	$147.82	13.357%	$167.5643	$167.56	$167.55	$167.60
Purchase #2	$83.74	6.465%	$89.1538	$89.15	$89.15	$89.20
Purchase #3	$190.71	8.364%	$206.661	$206.66	$206.65	$206.70
Purchase #4	$245.34	3.794%	$254.6482	$254.65	$254.65	$254.60
Purchase #5	$73.72	8.309%	$79.8454	$79.85	$79.85	$79.80
Purchase #6	$163.40	13.279%	$185.0979	$185.10	$185.10	$185.10
Purchase #7	$78.95	4.557%	$82.5478	$82.55	$82.55	$82.50
7 purchase totals =	$983.68		$1,065.5184	$1,065.52	$1,065.50	$1,065.50