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	$175.81	3.641%	$182.2112	$182.21	$182.20	$182.20
Purchase #2	$196.27	8.551%	$213.053	$213.05	$213.05	$213.10
Purchase #3	$209.31	11.463%	$233.3032	$233.30	$233.30	$233.30
Purchase #4	$30.75	3.275%	$31.7571	$31.76	$31.75	$31.80
Purchase #5	$178.32	12.414%	$200.4566	$200.46	$200.45	$200.50
Purchase #6	$162.35	3.787%	$168.4982	$168.50	$168.50	$168.50
Purchase #7	$240.36	11.842%	$268.8234	$268.82	$268.80	$268.80
7 purchase totals =	$1,193.17		$1,298.1027	$1,298.10	$1,298.05	$1,298.20