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	$89.42	3.830%	$92.8448	$92.84	$92.85	$92.80
Purchase #2	$73.40	6.835%	$78.4169	$78.42	$78.40	$78.40
Purchase #3	$110.70	12.523%	$124.563	$124.56	$124.55	$124.60
Purchase #4	$218.30	6.384%	$232.2363	$232.24	$232.25	$232.20
Purchase #5	$233.75	12.208%	$262.2862	$262.29	$262.30	$262.30
Purchase #6	$219.72	10.199%	$242.1292	$242.13	$242.15	$242.10
Purchase #7	$53.48	7.314%	$57.3915	$57.39	$57.40	$57.40
7 purchase totals =	$998.77		$1,089.8679	$1,089.87	$1,089.90	$1,089.80