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	$226.73	7.223%	$243.1067	$243.11	$243.10	$243.10
Purchase #2	$127.36	10.432%	$140.6462	$140.65	$140.65	$140.60
Purchase #3	$91.61	10.621%	$101.3399	$101.34	$101.35	$101.30
Purchase #4	$50.25	5.671%	$53.0997	$53.10	$53.10	$53.10
Purchase #5	$201.83	5.826%	$213.5886	$213.59	$213.60	$213.60
Purchase #6	$68.93	5.653%	$72.8266	$72.83	$72.85	$72.80
Purchase #7	$198.30	12.390%	$222.8694	$222.87	$222.85	$222.90
7 purchase totals =	$965.01		$1,047.4771	$1,047.49	$1,047.50	$1,047.40