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	$223.83	5.640%	$236.454	$236.45	$236.45	$236.50
Purchase #2	$41.52	6.780%	$44.3351	$44.34	$44.35	$44.30
Purchase #3	$159.52	7.535%	$171.5398	$171.54	$171.55	$171.50
Purchase #4	$156.77	7.663%	$168.7833	$168.78	$168.80	$168.80
Purchase #5	$50.75	8.321%	$54.9729	$54.97	$54.95	$55.00
Purchase #6	$102.78	6.344%	$109.3004	$109.30	$109.30	$109.30
Purchase #7	$137.93	5.275%	$145.2058	$145.21	$145.20	$145.20
7 purchase totals =	$873.10		$930.5913	$930.59	$930.60	$930.60