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	$176.59	5.411%	$186.1453	$186.15	$186.15	$186.10
Purchase #2	$37.37	11.148%	$41.536	$41.54	$41.55	$41.50
Purchase #3	$247.25	11.369%	$275.3599	$275.36	$275.35	$275.40
Purchase #4	$132.46	6.688%	$141.3189	$141.32	$141.30	$141.30
Purchase #5	$230.27	3.144%	$237.5097	$237.51	$237.50	$237.50
Purchase #6	$142.89	11.376%	$159.1452	$159.15	$159.15	$159.10
Purchase #7	$62.45	8.744%	$67.9106	$67.91	$67.90	$67.90
7 purchase totals =	$1,029.28		$1,108.9256	$1,108.94	$1,108.90	$1,108.80