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	$76.39	9.256%	$83.4607	$83.46	$83.45	$83.50
Purchase #2	$82.54	4.844%	$86.5382	$86.54	$86.55	$86.50
Purchase #3	$96.69	8.411%	$104.8226	$104.82	$104.80	$104.80
Purchase #4	$181.81	7.782%	$195.9585	$195.96	$195.95	$196.00
Purchase #5	$199.55	12.151%	$223.7973	$223.80	$223.80	$223.80
Purchase #6	$156.42	12.351%	$175.7394	$175.74	$175.75	$175.70
Purchase #7	$170.69	12.135%	$191.4032	$191.40	$191.40	$191.40
7 purchase totals =	$964.09		$1,061.7199	$1,061.72	$1,061.70	$1,061.70