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	$104.85	3.641%	$108.6676	$108.67	$108.65	$108.70
Purchase #2	$207.39	3.814%	$215.2999	$215.30	$215.30	$215.30
Purchase #3	$85.75	4.264%	$89.4064	$89.41	$89.40	$89.40
Purchase #4	$69.96	10.367%	$77.2128	$77.21	$77.20	$77.20
Purchase #5	$174.44	9.714%	$191.3851	$191.39	$191.40	$191.40
Purchase #6	$223.61	4.470%	$233.6054	$233.61	$233.60	$233.60
Purchase #7	$33.88	13.292%	$38.3833	$38.38	$38.40	$38.40
7 purchase totals =	$899.88		$953.9605	$953.97	$953.95	$954.00