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	$118.39	7.511%	$127.2823	$127.28	$127.30	$127.30
Purchase #2	$151.51	3.171%	$156.3144	$156.31	$156.30	$156.30
Purchase #3	$165.85	5.701%	$175.3051	$175.31	$175.30	$175.30
Purchase #4	$79.64	4.778%	$83.4452	$83.45	$83.45	$83.40
Purchase #5	$134.55	11.706%	$150.3004	$150.30	$150.30	$150.30
Purchase #6	$191.97	3.327%	$198.3568	$198.36	$198.35	$198.40
Purchase #7	$100.42	12.410%	$112.8821	$112.88	$112.90	$112.90
7 purchase totals =	$942.33		$1,003.8863	$1,003.89	$1,003.90	$1,003.90