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	$215.42	13.256%	$243.9761	$243.98	$244.00	$244.00
Purchase #2	$111.39	10.587%	$123.1829	$123.18	$123.20	$123.20
Purchase #3	$89.75	7.782%	$96.7343	$96.73	$96.75	$96.70
Purchase #4	$196.64	13.218%	$222.6319	$222.63	$222.65	$222.60
Purchase #5	$226.90	10.831%	$251.4755	$251.48	$251.50	$251.50
Purchase #6	$213.34	3.328%	$220.44	$220.44	$220.45	$220.40
Purchase #7	$172.50	10.736%	$191.0196	$191.02	$191.00	$191.00
7 purchase totals =	$1,225.94		$1,349.4603	$1,349.46	$1,349.55	$1,349.40