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	$147.30	7.643%	$158.5581	$158.56	$158.55	$158.60
Purchase #2	$37.35	6.758%	$39.8741	$39.87	$39.85	$39.90
Purchase #3	$215.30	6.497%	$229.288	$229.29	$229.30	$229.30
Purchase #4	$74.95	9.538%	$82.0987	$82.10	$82.10	$82.10
Purchase #5	$142.32	7.298%	$152.7065	$152.71	$152.70	$152.70
Purchase #6	$175.57	9.775%	$192.732	$192.73	$192.75	$192.70
Purchase #7	$47.52	8.402%	$51.5126	$51.51	$51.50	$51.50
7 purchase totals =	$840.31		$906.7700	$906.77	$906.75	$906.80