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	$191.77	9.732%	$210.4331	$210.43	$210.45	$210.40
Purchase #2	$64.76	10.616%	$71.6349	$71.63	$71.65	$71.60
Purchase #3	$113.30	13.478%	$128.5706	$128.57	$128.55	$128.60
Purchase #4	$164.73	10.817%	$182.5488	$182.55	$182.55	$182.50
Purchase #5	$173.71	4.747%	$181.956	$181.96	$181.95	$182.00
Purchase #6	$179.67	6.458%	$191.2731	$191.27	$191.25	$191.30
Purchase #7	$144.94	8.281%	$156.9425	$156.94	$156.95	$156.90
7 purchase totals =	$1,032.88		$1,123.3590	$1,123.35	$1,123.35	$1,123.30