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	$57.38	11.494%	$63.9753	$63.98	$64.00	$64.00
Purchase #2	$102.65	7.833%	$110.6906	$110.69	$110.70	$110.70
Purchase #3	$179.91	9.145%	$196.3628	$196.36	$196.35	$196.40
Purchase #4	$56.43	5.342%	$59.4445	$59.44	$59.45	$59.40
Purchase #5	$152.61	4.376%	$159.2882	$159.29	$159.30	$159.30
Purchase #6	$98.71	11.160%	$109.726	$109.73	$109.75	$109.70
Purchase #7	$224.71	4.368%	$234.5253	$234.53	$234.55	$234.50
7 purchase totals =	$872.40		$934.0127	$934.02	$934.10	$934.00