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	$149.71	9.715%	$164.2543	$164.25	$164.25	$164.30
Purchase #2	$91.65	5.705%	$96.8786	$96.88	$96.90	$96.90
Purchase #3	$105.96	3.756%	$109.9399	$109.94	$109.95	$109.90
Purchase #4	$197.38	6.732%	$210.6676	$210.67	$210.65	$210.70
Purchase #5	$116.62	13.112%	$131.9112	$131.91	$131.90	$131.90
Purchase #6	$89.99	4.575%	$94.107	$94.11	$94.10	$94.10
Purchase #7	$87.39	10.324%	$96.4121	$96.41	$96.40	$96.40
7 purchase totals =	$838.70		$904.1707	$904.17	$904.15	$904.20