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	$194.36	10.742%	$215.2382	$215.24	$215.25	$215.20
Purchase #2	$209.39	6.711%	$223.4422	$223.44	$223.45	$223.40
Purchase #3	$72.32	5.595%	$76.3663	$76.37	$76.35	$76.40
Purchase #4	$247.59	4.837%	$259.5659	$259.57	$259.55	$259.60
Purchase #5	$187.54	10.506%	$207.243	$207.24	$207.25	$207.20
Purchase #6	$156.49	10.776%	$173.3534	$173.35	$173.35	$173.40
Purchase #7	$38.82	7.160%	$41.5995	$41.60	$41.60	$41.60
7 purchase totals =	$1,106.51		$1,196.8085	$1,196.81	$1,196.80	$1,196.80