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	$116.71	10.515%	$128.9821	$128.98	$129.00	$129.00
Purchase #2	$218.89	3.400%	$226.3323	$226.33	$226.35	$226.30
Purchase #3	$59.30	7.792%	$63.9207	$63.92	$63.90	$63.90
Purchase #4	$135.42	4.478%	$141.4841	$141.48	$141.50	$141.50
Purchase #5	$229.37	9.233%	$250.5477	$250.55	$250.55	$250.50
Purchase #6	$162.75	6.560%	$173.4264	$173.43	$173.45	$173.40
Purchase #7	$147.47	8.240%	$159.6215	$159.62	$159.60	$159.60
7 purchase totals =	$1,069.91		$1,144.3148	$1,144.31	$1,144.35	$1,144.20