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	$106.45	5.139%	$111.9205	$111.92	$111.90	$111.90
Purchase #2	$72.70	6.757%	$77.6123	$77.61	$77.60	$77.60
Purchase #3	$248.60	7.505%	$267.2574	$267.26	$267.25	$267.30
Purchase #4	$172.59	9.742%	$189.4037	$189.40	$189.40	$189.40
Purchase #5	$168.27	4.216%	$175.3643	$175.36	$175.35	$175.40
Purchase #6	$152.45	12.359%	$171.2913	$171.29	$171.30	$171.30
Purchase #7	$101.64	10.275%	$112.0835	$112.08	$112.10	$112.10
7 purchase totals =	$1,022.70		$1,104.9330	$1,104.92	$1,104.90	$1,105.00