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	$42.69	8.251%	$46.2124	$46.21	$46.20	$46.20
Purchase #2	$110.54	6.798%	$118.0545	$118.05	$118.05	$118.10
Purchase #3	$178.64	7.454%	$191.9558	$191.96	$191.95	$192.00
Purchase #4	$180.45	5.745%	$190.8169	$190.82	$190.80	$190.80
Purchase #5	$49.25	6.825%	$52.6113	$52.61	$52.60	$52.60
Purchase #6	$144.56	12.337%	$162.3944	$162.39	$162.40	$162.40
Purchase #7	$224.73	10.595%	$248.5401	$248.54	$248.55	$248.50
7 purchase totals =	$930.86		$1,010.5854	$1,010.58	$1,010.55	$1,010.60