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	$159.62	9.458%	$174.7169	$174.72	$174.70	$174.70
Purchase #2	$68.76	12.413%	$77.2952	$77.30	$77.30	$77.30
Purchase #3	$149.89	4.632%	$156.8329	$156.83	$156.85	$156.80
Purchase #4	$96.56	13.792%	$109.8776	$109.88	$109.90	$109.90
Purchase #5	$205.50	11.709%	$229.562	$229.56	$229.55	$229.60
Purchase #6	$247.85	7.768%	$267.103	$267.10	$267.10	$267.10
Purchase #7	$123.50	3.368%	$127.6595	$127.66	$127.65	$127.70
7 purchase totals =	$1,051.68		$1,143.0471	$1,143.05	$1,143.05	$1,143.10