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	$148.89	12.761%	$167.8899	$167.89	$167.90	$167.90
Purchase #2	$208.86	5.747%	$220.8632	$220.86	$220.85	$220.90
Purchase #3	$55.91	4.550%	$58.4539	$58.45	$58.45	$58.50
Purchase #4	$150.96	11.858%	$168.8608	$168.86	$168.85	$168.90
Purchase #5	$127.38	3.416%	$131.7313	$131.73	$131.75	$131.70
Purchase #6	$118.96	11.855%	$133.0627	$133.06	$133.05	$133.10
Purchase #7	$137.39	8.761%	$149.4267	$149.43	$149.45	$149.40
7 purchase totals =	$948.35		$1,030.2885	$1,030.28	$1,030.30	$1,030.40