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	$208.67	7.292%	$223.8862	$223.89	$223.90	$223.90
Purchase #2	$58.60	10.596%	$64.8093	$64.81	$64.80	$64.80
Purchase #3	$217.34	9.850%	$238.748	$238.75	$238.75	$238.70
Purchase #4	$86.76	10.494%	$95.8646	$95.86	$95.85	$95.90
Purchase #5	$54.91	13.470%	$62.3064	$62.31	$62.30	$62.30
Purchase #6	$162.32	7.201%	$174.0087	$174.01	$174.00	$174.00
Purchase #7	$199.72	12.411%	$224.5072	$224.51	$224.50	$224.50
7 purchase totals =	$988.32		$1,084.1304	$1,084.14	$1,084.10	$1,084.10