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	$184.25	4.403%	$192.3625	$192.36	$192.35	$192.40
Purchase #2	$57.33	12.269%	$64.3638	$64.36	$64.35	$64.40
Purchase #3	$163.84	11.428%	$182.5636	$182.56	$182.55	$182.60
Purchase #4	$187.68	4.775%	$196.6417	$196.64	$196.65	$196.60
Purchase #5	$93.96	5.240%	$98.8835	$98.88	$98.90	$98.90
Purchase #6	$147.34	8.773%	$160.2661	$160.27	$160.25	$160.30
Purchase #7	$99.36	9.575%	$108.8737	$108.87	$108.85	$108.90
7 purchase totals =	$933.76		$1,003.9549	$1,003.94	$1,003.90	$1,004.10