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	$211.64	5.441%	$223.1553	$223.16	$223.15	$223.20
Purchase #2	$73.95	11.459%	$82.4239	$82.42	$82.40	$82.40
Purchase #3	$76.99	7.348%	$82.6472	$82.65	$82.65	$82.60
Purchase #4	$86.59	3.207%	$89.3669	$89.37	$89.35	$89.40
Purchase #5	$246.94	6.569%	$263.1615	$263.16	$263.15	$263.20
Purchase #6	$172.42	11.684%	$192.5656	$192.57	$192.55	$192.60
Purchase #7	$178.72	12.684%	$201.3888	$201.39	$201.40	$201.40
7 purchase totals =	$1,047.25		$1,134.7092	$1,134.72	$1,134.65	$1,134.80