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	$90.87	12.687%	$102.3987	$102.40	$102.40	$102.40
Purchase #2	$160.27	11.414%	$178.5632	$178.56	$178.55	$178.60
Purchase #3	$78.93	4.262%	$82.294	$82.29	$82.30	$82.30
Purchase #4	$5.82	5.134%	$6.1188	$6.12	$6.10	$6.10
Purchase #5	$194.67	10.470%	$215.0519	$215.05	$215.05	$215.10
Purchase #6	$175.28	4.257%	$182.7417	$182.74	$182.75	$182.70
Purchase #7	$76.71	7.581%	$82.5254	$82.53	$82.55	$82.50
7 purchase totals =	$782.55		$849.6937	$849.69	$849.70	$849.70