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	$226.59	7.658%	$243.9423	$243.94	$243.95	$243.90
Purchase #2	$240.29	6.454%	$255.7983	$255.80	$255.80	$255.80
Purchase #3	$133.95	9.606%	$146.8172	$146.82	$146.80	$146.80
Purchase #4	$93.90	4.239%	$97.8804	$97.88	$97.90	$97.90
Purchase #5	$129.34	10.223%	$142.5624	$142.56	$142.55	$142.60
Purchase #6	$69.42	13.280%	$78.639	$78.64	$78.65	$78.60
Purchase #7	$89.63	9.694%	$98.3187	$98.32	$98.30	$98.30
7 purchase totals =	$983.12		$1,063.9583	$1,063.96	$1,063.95	$1,063.90