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	$111.93	3.530%	$115.8811	$115.88	$115.90	$115.90
Purchase #2	$172.89	11.833%	$193.3481	$193.35	$193.35	$193.30
Purchase #3	$127.35	11.727%	$142.2843	$142.28	$142.30	$142.30
Purchase #4	$174.93	11.437%	$194.9367	$194.94	$194.95	$194.90
Purchase #5	$201.67	4.176%	$210.0917	$210.09	$210.10	$210.10
Purchase #6	$153.88	11.190%	$171.0992	$171.10	$171.10	$171.10
Purchase #7	$31.91	3.842%	$33.136	$33.14	$33.15	$33.10
7 purchase totals =	$974.56		$1,060.7771	$1,060.78	$1,060.85	$1,060.70