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	$179.99	11.621%	$200.9066	$200.91	$200.90	$200.90
Purchase #2	$38.69	8.771%	$42.0835	$42.08	$42.10	$42.10
Purchase #3	$118.96	7.571%	$127.9665	$127.97	$127.95	$128.00
Purchase #4	$244.29	3.586%	$253.0502	$253.05	$253.05	$253.10
Purchase #5	$74.51	4.790%	$78.079	$78.08	$78.10	$78.10
Purchase #6	$250.80	5.356%	$264.2328	$264.23	$264.25	$264.20
Purchase #7	$54.60	7.796%	$58.8566	$58.86	$58.85	$58.90
7 purchase totals =	$961.84		$1,025.1752	$1,025.18	$1,025.20	$1,025.30